Hmm as England (well UK) I had that infamy of around 30. I guess my limit was high lol.
Sounds like your problem may have been war weariness. For everyone to rebel and to have such a high chance of rebelling it seems likely. As for everyone attacking you, I found with the UK that happened a lot because of chain alliance. The Irish kingdoms have a nasty habit of picking very good allies. Allies who are usually allied with A LOT of other people. For instance when I took one of the Irish kingdoms their ally was Brittany who were allied with Sweden, The Hansa ect ect which meant I had around 10 nations at war with me all at once. I learnt as England that you do have to be careful. Abandon/sell off your continental provinces, unless you really really want to focus on that, and focus simply on the UK. Don't attack Scotland unless you can lure them into a war of some sort but I'd definitely recommend against initiating it. Usually when one of the continental powers decide to attack you Scotland will join in. I then made sure to make peace with the continental power ASAP leaving me to focus on raping Scotland from a defensive standpoint. If you initiate it you will definitely get a lot of continental powers on your arse. Only attack one Irish kingdom at a time and be prepared to have a chain alliance invading your shores. I generally kept an army in England and an army in Ireland. I also slowly worked on my navy until my UK defence fleet had about 40 caravels. Once I reached that level I was never invaded again. After my colonial expansion I had about 200 ships
O and early game with England I hardly had any money because of the constant wars and having to maintain a very large anti-invasion army.
I focused on offence because I always tried to make sure my armies were larger than the enemies, generally meaning they wouldn't attack me so offensive made sense for me. I also went with quality and it seemed to work.
Regardless, early UK is pretty intense because of the constant invasion/Scotland issue. I had to reload saves several times because I played it wrong and ended up having my armies wiped out by invasion forces. Once you build that navy though you are set because as soon as you go to war you can set the fleet to patrol from Ireland to Eastern England, stopping any invasion force.