OP is sabotaging his future employment prospects by taking the firing so personally. For whatever reason it wasn't a good fit. It's not professional at all and

OP is sabotaging his future employment prospects by taking the firing so personally. For whatever reason it wasn't a good fit. It's not professional at all and speaks badly on your character and appears immature. It shouldnt be a revelation that culture changes when you go from 10 to 100 employees. He doubles down on this by making financial decisions based upon his hurt feelings, like he still holds a grudge and isn't over it. Who wants to employ someone like that?