When it comes to the Internet I don't feel couples need privacy. If you want to diary or journal your feelings, buy a journal and write in it at home. There is too many ways to get in trouble on the net. I understand his desire to check up on you... and because you got angry and claimed "privacy" he now is claiming the same. Tell him you are sorry that you acted this way and that anything you do online is free for him to read, check, etc... Don't write or do things online that he can't know about it.
Buy a nice journal to write in at home and have a special place to keep it. To not trigger his curiosity, I would choose to write in your journal when he is not home so that it doesn't become a "curiosity" issue.
Couples go through phases where they argue a lot and then it smooths out and then starts again. You are wise to worry about this rift in your marriage and the consequences it can have. Make peace w/ your man.
About his cuddling and your need for space. Compromise- cuddle some, and have some space. If he wants to cuddle and you want space he will view this as rejection, so cuddle for a little while and then get up and go do whatever you wanted to do.
My husband used to do this thing I HATED. He'd block my path when I was going down the hall or was in the kitchen and would stand there until I hugged and kissed him. Sounds fast enough but he'd sometimes want to chat for a minuet, etc and this TRIGGERED me because I felt like I could NOT get by unless I submitted. I HATED That feeling. We had a talk and he stopped doing it thank GAWD! He does like to snuggle, etc more than I do, but we compromise.