living seperated in fmh-how to split finances

Hi.wonder if anyone here is living long term with stbx and kids because of very poor financial situation on both fronts(see my other post for details).having looked into financial costs I cannot afford to rent and live in a place where I can have room to house my kids( I have a short term offer to house sit elsewhere but I have realised that would be just that a short term solution with longer lasting impact).my stbx is adamant she doesnt want to sell the FMH so I feel my only choice is to stay in the FMH. I could convert the loft space to a sleeping space( currently on the couch 5 months in)...does anyone have a similar situation? How do u split finances?
At the moment both our earnings go into a joint account but I think it would be clearer to change this.at the moment I pay all bills etc petrol food child costs

Give one good reason why your stbx would want this set up to change. You are the work horse at the moment providing at will. She doesn''t want you but your money is good enough. Separate the finances mate and pay your quota as per CSA. You are not a ''couple'' anymore. Might change her thinking a bit towards what kind of future there is for the two of you. Cake and eat it springs to mind.