Just looking at the language you are using makes me wonder if there is a long-standing pattern of financial abuse in your marriage. I’m guessing he’s the one who introduced the notion that wanting your fair share of the family finances was “sponging off him”. And the fact that he put the house in his name alone when you’re married, attempting to deprive you of a marital asset?
Do you currently have equal access to the money you jointly earn, or only what comes from your job?
As others have said, it’s only ENM if you both agreed to it, and opening a marriage only happens by consent - the fact he did so 3 years ago means he was cheating, but this is probably how he’s justified it in his own head. And of course he wants to stay together: he knows how much a divorce will cost him financially in terms of the house, pension, etc. I am also sure that he wants you to stick around to keep house and eventually care for him when he’s too old to go raving any more and needs someone to manage his meds and wipe his arse, because his 20-something raving buddies aren’t going to want to do that.
Well fuck that. Find your anger. Without your work he couldn’t have earned the salary or paid for the house or generated his pension fund. Just because he’s trained you to think what you have done as his wife is worthless and not an equal contribution doesn’t make it true.
I am so sorry for the additional trauma you have been through that has caused you to question whether a solicitor is worth it. There are some excellent ones out there who also genuinely care and enjoy sticking it to people like your husband. So do some research. Talk to a few different ones for an initial consultation and see if one of them inspires confidence and seems outraged on your behalf. Talk to Women’s Aid about financial abuse and see whether it rings true for you: financial abuse would allow you to get legal aid for your divorce, which would mean you could afford it.
And while right now you’re lost and hurting from the betrayal, I can guarantee that you are worth knowing, and have plenty to enjoy once you’ve offloaded your cheating husband. You will be able to make friends, and you will be answerable only to yourself for what you want to eat, do, watch on the TV. And you have a dog who will be better company than your horrible ex H.
Grieve now. And when you get angry, channel that into looking into your husband’s finances and getting evidence together so he can’t hide anything in the proceedings. Right now he has so much more to lose than you, and you have everything to gain now you know what a faithless shit he is.