You dont say how old the child is?
Or what your income is, his income or your ages.
As even if he is 3X your salary, if you are on 6K a year and he is on 18K- that isnt massive and as the marital debt will have to be cleared from the assets that only leaves 75K. I think him giving you 30% seems fair- but fairness is all perception and a matter of opinion
Can I ask, did he want the divorce? Was it mutual? As if not, you can understand his resentment in the fact that you are basically trying to stake claim in something that wasnt ''earned'' through the marriage. This was a gift from his family to him (not both of you) so its a bit like rubbing salt in the wound but you divorcing him and then trying to take half.
Could you not work full time? Can you maximise your income? Are you getting CTC and WTC?
Im not sure legally where you stand as I had a friend who also paid for his house with inheretence- it is now occupied by his ex wife.