It sounds like he’s religious, so getting married under those circumstances is common and their marriage may be great. There’s a feeling you’re having about your feelings about yourself and relationships that is the reason why you are feeling resentment toward his marriage and also are at the age where all friends seem to be coupling.

You thought he’s using you by sending you an invitation. What would he be using you for, a gift? If you don’t want to go, you don’t have to. You didn’t have a fallout with him and were once a very close friend, so I think congratulating them, a card, a gift/ attend or not attend. Will there still be a pandemic? Social distancing is a great excuse.

It also sounds like you and he had some other issues when you were friends. You shared an abuse situation, he tried to drag you back into religion. All your feelings on this are valid.