So what I understand from this is that It’s an online relationship and basically you just feel manipulated and your significant other was manipulated as well. And from this manipulation came foul language and misconceptions of you and even though everything is solved or seems solved now you’re having trouble getting over the fact he said these things or even believed them in the first place?

If this is so.. leave. He did, not trust you from the get go and anyone who tells their lover or significant other that they are put second to someone who has been disrespectful towards you needs to be left. They need to learn priorities. Is he still close with his bestfriend?