Actually, I am surprised that stake offers something like deposit bonuses now, I never heard of that. Thought this might be a scam but since you say the bonus money was added to your account I guess it's not.
Anyway, I had the same problem with being limited on sports. This limit is mostly just for 1 sport, the one where you obviously have been successful, otherwise you wouldn't have gotten the limit.
I mean you could just run the required wager through the casino at like super high winning % bets, that would be a solution. Dice 1.01 odds for example. Sure you would have some calculated losses due to house edge but it's better than nothing. Or, as I said, you try to bet on different sports and check if the limit also applies there, normally it shouldn't.
Hopefully you can figure something out! Good luck!
Stake has deposit bonus off course and that is for new accounts and with registered code it through the code that you get the bonus through your first deposits, so don't mistake the deposit bonus on stake to mean that you get bonus each time you make deposit, I remember stake become the second cryptocurrency casino that I received welcome bonus aside from Bc.game that also give me some welcome bonus also.
It a good way to start at a casino and sure those money helps alot most especially if you lost your initial deposit, you still have something to play with.