go to counselling yourself OP? you've been together for 17 years and I wouldn't be saying 'ah well' after 17 years but doing all I can to see if the relationship can be saved (though not at any cost). only you can know if those 17 years have been valuable (worth saving) or crap (not worth saving). don't want to get into the wrangle above (though SO could!) but imo (or ime) it's not a doddle starting again.
of course if your relationship has always been poor, or damaging, then, yes, this would be a time to look at splitting in order to have a better quality of life in the future. whatever way, imo 'professional' support is essential to manage this huge transition - and also essential if you stay in the marriage: both options can be very difficult and very probably need some professional input to pull off as effectively as possible.
looks like dh is not making a lot of sense, which can be very destablising for you. you also say you have had hideous rows so it doesn't sound as though you are in a position to be able to talk sensibly together at the mo. Maybe now is not the time for you both to go into counselling together anyway (even though he refuses) but it may well be a good time for you op - I honestly don't think this situaiton is going to resolve on its own. I think I remember your other thread and from what you say there, things are very fraught indeed between you at the mo.
if you decide to split, imo this is a HUGE decision, particularly after 17 years, as not only will you two be affected but there are many people whose lives are going to be either directly or indirectly affected to varying degrees by that decision, so your decision about the future is not just yours. that's not a guilt trip but reality imo. If the relationship is indeed toxic (and always has been) then you do need to get out, even though a split may adversely affect other people. But I do bridle at suggestions/advice that ah well you're not happy, he's a dick, get rid, knock it on the head and try again somewhere else... 