Tell ds's father you are ending your relationship, the reason being he treats you like shit.
(Which he does because he is a bully and thus a weakling who picks on nice people who don't expect the father of their child to be an arsehole)
Tell him you very much want him to see lots of your ds. You and he will arrange access between a) just the two of you or b) via your solicitors. His family will not enter into this.
You tell your gp you are ending your relationship but you feel very stressed and have realised you have problems with confidence and self esteem, and would like to talk to someone about this.
He doesn't need to see why you've got a solicitor. If he doesn't get one, more fool him.
What you really, really, really need to do is stop letting what you think he'll do influence your decisions. Work out what you want for you and your ds. If you make decisions now based on what your ex does/says, then he is still controlling you.
I think the reason you might sound "half hearted" is that you genuinely don't realise how you can do this. I think you're uncertain of the steps to take.
The questions to ask are the ones that start 'How do I...?' not 'But what if he...?'
Good question: What do I say to the gp? (practical, how to get something done)
Crap question: Won't it make things harder if I get a solicitor? (THings are already hard and sod what he does, you're getting a solicitor for you and your ds)
From your last post, I can see you are a strong woman who is determined to make life better for herself and her child. At 2, your ds won't be too affected by the break up, he's still very young. You are doing the right thing.
So hurray for you!