Hi again, sry for the little delay!
-I want to note first that re-shoving 25bb eff. BTN vs CO with the range u've given is way, way too loose. I can't give you an exact range unless we speak with numbers-pay out, people left, stack set up, but in general, it's gonna be way too loose. With position, you can just flat with the part of your range that plays well IP postflop, but would be otherwise minus EV on a shove. You can also 3bet/fold with the small pairs and some small Axs.
1-I have a re-shove range from every position with 20bb or less, but ranges will change drastically
2. Usually around 20-22bb effective, but there is so much more to do. General strategies are not optimal. That's the short answer. I give u an example. U have a loose fish on the BTN, who will open 50% of hands, but also call very loose on a shove. Any Ax, any pair, most broadway. Then shoving a hand like TJs for 20bb becomes suicidal. However, flatting would be great. Your hand plays well postflop vs his range and it's way too strong to fold. Pushing 44+ however will be really good usually(say risk aversion is small) because of his extended raise/call range. You can flat, 3bet/fold, 3bet/call even down to like 16-17bb. Your decision comes to whatever you think it's most profitable. If you f.e. think that villain raises a very wide range, aggro postflop but will call on a shove with a very tigth range, then again re-shoving AA/KK/QQ will be bad. Best would be to flat and exploit his tendencies.
3. It comes again on what's most profitable. It is reasonable to 3bet/fold 22-33 25bb f.e. if you think villain will fold a lot, but only push the power hands in his range. You can also add more bluffs to it, then re-adjust if needed and so on. If villain is an aggro reg who will be 4bet light, then 3betting non all in with 44-55 25bb for value will become more profitable than shoving, because villain is not gonna call as loose on a shove, then what he would 4bet on a 3bet. Espeially vs regs, meta and game flow are very importantn.