Ok, I think you may have just bought the wrong gear for your bike...

You bought mudguards, but really, they don't belong a road bike. If it were a mountain bike, cross or even hybrid, then that's a different story that may make sense.

But for a road bike, it's overkill and you'd be much better off with proper fenders, IMHO.

In any case, from your pics, it definitely seems like the downtube mudguard isn't well suited for your particular bike. Either the cable or the strap (or both) will fray at the point of contact and prematurely fail.

You may be able to jerry-rig an alternative mounting solution, or change the mounting placement - it's impossible to tell without physically being in front of the bike.

As for your saddle bag, it should hang underneath your seat - but first you'll have to get rid of either the mudguard or your taillight because that area isn't big enough to accommodate all 3 things.

If you replace the mudguard with a proper fender, you'll be able to move the mount for your taillight to the bottom of your seat post, flip the light so it's hanging down and have plenty of room for the bag.