What are some good exercises to do, that will help you increase what you can pull, and help you to practice longer?
I think pushups are the best?

lmao i love those quotes in your sig! as for exercises you can try pull ups too because they really work your back and shoulder muscles that you use to draw and hold it...i also think just shooting your bow a lot helps

A restrictive row machine will actually work better than the push up since pushing up works your triceps and pulling a bow will be your shoulder, back, bicep, and forarm...
There is a machine I use at the gym that kinda resembles a row.. but you sit in a chair and pull back the weight towards your body...

You could get light dumbells and do one arm rows, or any shoulder and back exercises. Push ups would help alot too, trust me I do a lot of push ups in the army and I have no problem shooting for a long time.

Never used one but you could try a bowfit..