As someone who wasn't socialized to stuff down his emotions and did often get bullied because of it, I learned two things, firstly how to control that emotional response, and, secondly, how to hurt or kill threats. There's no crying here anymore, only steely-eyed resolve. In that situation, and I've been in them (I recall using my bike pump as a billy club in one instance), I look for a weakness and take them out if possible. Let their loved ones cry over their deeds of violence and sociopathic battery on society..
In light of everything above, I think the OP is being judged far too harshly. I mean, sure, she’s young and naпve, and her behavior is definitely a bit shady, but her bf’s behavior seems even worse - it’s controlling, and I could even see it leading to physical abuse. I’d urge the OP to consider leaving her bf if the snooping and constant prying don’t stop, especially after she’s made efforts to balance her time with them more fairly. I mean, her behavior is far from ideal, it sets off red flags that her bf has every right to be concerned about, but to me it doesn’t ‘cross the line’. The snooping and constant prying however, imho, are behaviors that definitely cross the line as to what is acceptable in a relationship, and have the potential to escalate into something much more serious..