I've had your first race up on a tab since you posted, and I've looked at it now and again.
Based on your riding the rest of the clip it seems that you're able to get closer to the riders, but you seem to sit to the left of them, instead of behind them. If you sat, say, a foot to the left, instead of 5 or 6 feet to the left, then you'd get some benefit from the draft.
You go wide in the turns, pretty consistently. I'm not sure if you're uncomfortable on the bike (maybe not enough weight forward? Are your bars high? Do you have a shorter stem? Are you on the hoods?) or you're not comfortable with cornering?
In at least one of the turns I see the bots dot thing, yellow reflector. Once you know where they are they might as well be as big as a car, you can always carve a line that goes right next to them. It's not necessary to go outside of it, you can go inside.
If your front wheel seems like it's chattering or not getting great traction over the bumps/seams in a turn, you can think about reducing pressure (if you have a lot of tire pressure) or you can think about putting more weight on the front wheel. I slide forward on the saddle, I hold the drops, and I have a lot of weight on the front wheel. Once that front wheel has some weight on it you can turn really hard. If you don't have enough weight on it then it's very hard to go fast in a turn.
For me the optimal stem is about 12 cm long for regular bars, 15 cm for compact bars. You want your hands to be somewhere near vertical from the front hub. If your hands are more like over the brake then you won't have much weight on the front end.
At 3:55 there's a guy on the inside that swerves out left before turning right. That's an extremely dangerous move. Don't do this yourself and stay away from that guy. If that was near me I'd say something to him, but in a 5 race it's hard to be "the expert" because everyone is learning.
The turn at about 3:20 seems to intimidate you. You back off, you aren't next to anyone, and everyone goes a bit faster. On that lap I'd have checked to the inside, made sure I was clear, then moved in to follow whoever was on the inside.
In general you can look down to check if you can move over a bit. Even if the riders aren't very close to each other in your area you should still be "on a wheel". Don't be 10 feet away from everyone else.
I like the above picture because it illustrates a few things. I'm the one in red/black EXPO kit. The guy in front of me is a multi-time Masters National Champ (crit, track), Pat. The guy in front of him is also a multi-time Masters National Champ (crit, track), James. James doesn't like sitting on wheels, and in fact he does some interesting things like he'll ride the whole race in a 53x11. He's super strong.
Pat, on the other hand, is an extremely shrewd racer. He'll do a few races a day (M45, M55, Cat 3) and try to do well in each. This means saving energy for each race to optimize his chances of doing well. Therefore he's sitting pretty close to James.
I'm weak so I have to sit in. I'm sitting on Pat's wheel.
Note how we're all staggered to the right? The wind is coming from the left, i.e. from where the camera is, and shelter is to the right.
Now look at the other riders in the picture. The rider in orange is in the wind. The rider obscured behind him is not. The rider in blue/white is in the wind. The rider behind that one is not. Even James, who doesn't like sitting super close to wheels, is to the right of the guy in orange and a bit to the right of the obscured rider, so he's getting some shelter.
So wind is key here.
I do trust Pat pretty well to hold a good line. I am comfortable being close to him. James, in this situation, is realistically a good wheel also, and Pat trusts him. I'm super sheltered, I'm sitting on a wheel,
even though other riders around are not sheltering.
My point here is that even at the back of the field, when everyone is sort of fragmented (like at the beginning of your race) you should be ON a wheel. Don't be a fragment. Get on a wheel. Maybe ride a foot to one side, and peek up the road. Go from fragment to fragment, but always get back onto a wheel.
You make some big digs at 700-800w so you can make such efforts. You'll want to make them if you need to cross a 30 or 50 yard gap. Don't sit at 300 or 350w doing nothing. Sit at 200w doing nothing then make a 700w dig. Then when you're done with the dig immediately get on a wheel and go back to 200w (or less).
The corners. You need to work on your cornering. You can practice when you drive, when you push a shopping cart around, even with little toy cars at your desk (I used to keep a dozen Hot Wheels and Matchbox cars at my desk to "play cornering"). You'll want to practice cornering to the inside (maybe a foot inside?) at these reasonable (24-26 mph) speeds. At 30-35 mph it'll be tougher, but the basics are the same. Learn at lower speeds, apply at higher speeds.
Try not to brake. On the bike try to weight the front end. Do practice loops in a development, maybe near your house, maybe in a parking lot? Should be empty and ideally have a shallow hill with a corner/curve at the bottom. A shallow hill will let you get to 25 mph without having to work hard, and in fact you may have to brake to keep from going over 30. This is not a fitness workout, this is a technical one. If your heartrate doesn't go above 140 bpm that's fine, it's not necessary. You wan to focus on form, on a cornering line. Practice turning at 25 mph, getting close to the curb/inside, weighting the front end, less and finally no brakes. Practice both lefts and rights. Try sticking your knee out, try it without sticking your knee out. Inside pedal up. Then, on a flatter curve, pedal through the turn, at first in less sharp turns so you don't dig a pedal.
When stopped get off the bike, put the inside pedal down, and lean the bike over until the pedal hits (make sure pedal is right side up). This will give you an idea of lean angle before digging a pedal. Check contact point. If contact point is not metal then you can realistically dig a pedal pretty hard with no problem. If/when you're off the back of a race pedal through turns. If you dig a pedal no harm done, you rarely crash from it (just don't do anything, just keep riding the bike). It's good to know about how far over you need to be to dig a pedal. It also teaches you that you can pedal through many turns with no problems.
Pedaling through turns may not be "recommended" by some people, but for you it'll have a different effect. If you're pedaling you probably won't be braking, and that's what you want, to not brake automatically when you corner. It should improve your speed through the turn even if you're not pedaling hard. When off the back or off the front pedaling through a turn can be very helpful.
more random stuff:
At 13:00 or so you're doing great. You're on the wheel of the rider in front, and you're pretty steady. Then you swing out left and go to the front. Although they may not have been going fast enough you realistically don't want to just jump to the front.
You do a massive turn at the front until you catch the UC Irvine guy. Then you go wide in a turn (are you pulling off? if so wiggle your right elbow in that situation, let the riders by on the right). I definitely would have been cooked after that pull. Typically, in a group of 4 to say 8 riders, a 20 revolution pull is sufficient. Do 20 revs, wiggle the elbow that you want the riders to pass on, and move over gently the other way. In this case you pull, wiggle right elbow, move gently left.