If your position has your knee over the pedal spindle, you can move the seat back a bit so your knee is 1-2cm behind the pedal spindle. That engages the glutes more, especially when climbing. It's not going to take a slow climber and make him fast however.

I set foot angle by paying attention to my feet while I ride. If it feels like I want to rotate the foot to a different position I adjust the cleat to allow it. Everyone is different but most likely your best position will have your knees more or less in line with the pedals, neither bow legged or hitting the top tube all the time. Heels in makes you more bow legged, heels out moves the knees in.

I don't beleive that a recreational rider needs to do big gear repeats. (I'm a racer and don't do them). Unless you have a good base and strong knees from years of riding you are more likely to injure yourself, and the training benefit over just riding hills is not all that appropriate for recreational riding. If it even exists at all- there is a big argument among exercise physiologists if big gear repeats have any benefit at all vs self-selected cadence. Your limit right now is your endurance base, so just go ride more. Include hills of course if you want to work on your climbing.

10%/week is a rough guideline. Some people can do more.