Don’t know what to do

Hi Everyone, this is my first post, so please bare with me ?

My partner and I have been together 8 years and have a child together. 
We’ve already had a rough relationship and if it wasn’t for our child probably would have ended 5/6 years ago. 
For context… he was talking and meeting other women when I fell pregnant and shortly after. We managed to just about work through this as we were both mentally in a bad place, arguing a lot and young having an unplanned child. Worked through trust and emotional issues.  

We worked through his debt that caused him a lot of issues in every way. Debt he caused before we met.

We were living together at parents house- couldn’t afford to move out. However, we argued (when I found out about another women), my father got involved (I know he shouldn’t have and he was asked not to) and we haven’t lived together since. Although my parents and him are fine since.  
We have been staying between houses. We’re at our own homes during the week and mostly his parents at the weekends.

He can’t move in here as my parents now have an animal that we found he is very allergic too and his parents is too far away for us to move to. It would mean a change in job and school. 

We had been in a really good place relationship wise. And finally were able to make the next step to moving out. We were in the process of buying a new build, put the money down, paid for what we’ve had to. When the mortgage lenders found his gambling which I knew nothing about. I found out through them. This caused the Lenders to pull out but only ‘for now’. Because the gambling was only from November, they said they were happy to proceed if he could stop and prove it. That they just need the next 3 months statements to be clear. However, the new build developers have refused to wait and want to sell asap (even though it’s not complete until Jan) which I understand but has also annoyed me. Our child is heart broken, that they aren’t going to have a home with their Dad. 
I confronted him about it and he was honest. I mean I knew he did the odd lottery ticket and a tenner on football here and there but not to the extent it has actually been. 

He stopped immediately. Has cancelled all accounts/ apps (which is was all done through). He has not stopped apologising since. Admitted he has a problem and is willing to do whatever to fix it. 

I don’t know what to do going forward. 8 years and a child. Part of me is saying support him, work through it. Part of me is saying walk away. I feel more hurt over this than I did the rest of our issues. 

Apologies for this being so long!
Any advice/ guidance is appreciated.