Ursch is indeed scary. I'm not sure if yandere is the right word for it, but it's the closest I can think of. And Isabella is just a dummy in love. I'm just glad she knows to draw the line at domestic violence, infidelity, and gambling. Switch gambling with any other addictive vice and you've pretty much covered all the big red flags.
Their dynamic...fits, for better or for worse. And they indeed make good decisions to prioritize a healthy romantic relationship. It'll probably work out because they both desperately and realistically try to make it so.
More importantly, Ursch is somehow just as OP as Isabella, which is...unexpected. I guess he would be if he's he one that supplies you with all the crazy items in the game.