You should try to calm down until your infamy goes back to less than 5 or so. That's for your current situation btw, if you had no threats like austria just next to you, you could start another war sooner.
When you are at peace, you should try to keep your inflation at a minimum, and if possible decrease it.
A few tips :
- Always concentrate your research funding on one research at a time
- Always keep your treasury slider at a minimum
- At peace you can decrease your land funding to spare gold
- Never ever stay over your force limits at peace
- I personally don't recruit mercenaries, you are much better sparing your manpower and being sure your actual army will reinforce quickly.
- The AI is dumb in very many ways, one of which is that they always use war taxes. You don't have to and especially with difficult wars you shouldn't as that way you only need to survive a long war to win, because your enemy will be sinking in rebels after a few years.
- in EU3 DW the key to making successful wars against AI countries that are more powerful than you is to lure them into high defense bonus provinces that you control, then bringing massive reinforcement when the battle starts.
- If you own imperial provinces for which you don't have cores, your first priority is to get a magistrate to remove each of them from the empire. If you are an empire state yourself, you shouldn't be expanding in the empire. If you still get this horrible popup where basically either the emperor takes your province, either it becomes a ruin up until the end of the game, you can save and reload your game without answering to make the popup dissappear. But that's cheating.