Hello and welcome. It sounds like a really tough time for you.
How supportive are your parents of you and your baby? *IF* you decide not to go back, will you be comfortable staying with them for a while (months or a couple years even) as you sort this out?
He is in my thoughts all of the time. I'm afraid of what he will say when he finds out that I have met my friends for coffee (inevitable question of who knows what and who did I talk to and what did they say) Everything I say I run through the filter of what will he say? Will this annoy him? Will this anger him?
Acknowledging that you are afraid like this is a good starting point.
May I ask specifically what you are afraid he might do or say?
I so badly want to believe that it'll all be fine, but I know that it probably won't. How do I go about trying to reconfigure all of my plans to this new reality?
Chances are he won't be getting better--he won't magically stop doing what you are afraid of. (See above question... .)
Some things, you have the power to protect yourself from while staying in your marriage. This isn't easy, but it is possible, and we've got the tools to help you here on this site. (Again, specific problems are better for us to support you.)
My suggestion--while you are living long-distance, work on what you can do to improve your r/s with him at this distance, and evaluate how that is going before you return--I expect that going back with a new baby will add stresses and make things worse, at least in the short term, so don't do it until you feel more comfortable with your new skills and tools.