Quite frankly you HAVE - albeit indirectly - contributed to HIS deposit by paying his share of rent and bills!
I think you may have posted about this cocklodger before?
DO NOT let him keep shirking his financial responsibilities in YOUR home - quite honestly I'd be presenting him with a Fucking bill for his share of the rent & bills since he's moved in with you!
And DO NOT give up you and your child's home for this selfish tosser!
Either he does a total about face and stops taking advantage of you or he fucks off!
Sorry, but he has used you to save up for his deposit and you've let him. He's now offering you nothing in return. very accurate summary of what's happened! He's taken you for a mug!
You also don't want the same re marriage & children? DUMP HIM.
Why are you putting up with this?
"OP I wouldn’t put it past him to use your place as a helpful base while he renovates and then cut his ties after that." Can absolutely see that happening he's a total shyster!
"but people do these things after months sometimes weeks. What happened to love at first sight?" NOT if they're sensible and DEFINITELY NOT when there's a child in the mess!
"it takes an amazing person to step up to the plate of raising another mans son." Does he do loads of sole childcare? Only way you could possibly justify that you've essentially paid him to do this.
"however he loves him and fathers him like any real good father would" no he didn't! "Real good fathers" pay to support their children, they DON'T take money away from the mother of that child and so deprive the child!
"Of course I'm aware that he is technically 'sponging'" no not "technically" he IS a total sponger - how much is even 1/3 of your rent & essential bills?
For your child's sake you need to stop being so naive and gullible!