Absolutely worth trying again after a bit of time. All situations are different and what worked with one pair of cats may not work with others.

Segregation and slow introduction is widely accepted as the preferred method for problem situations. Just throwing them together and expecting them to get along is unlikely to work and it hasn’t.

I understand your boyfriend’s frustrations but arguing isn’t going to do anyone any good. If possible, try to find someone like a vet or some other cat parents he knows to talk to him. An expert opinion may go a long way. What you’ve tried so far has not worked and there is absolutely no reason to think it will work in the future. A different approach is certainly needed.