You make it sound as if your "job" is just to hang around in case he needs you as a friend; that's not what friends do! Friends live their own lives and, if they do need their friends, they reach out for them and the friend is there or not each particularly time, depending on their own circumstances.

Each person gets to decide what they feel they are getting from a friendship and whether they want to continue being friends with that person. Not being "friends" does not mean you dislike each other or the other cannot call on you if they wish, it just means that you have other things going on in your own life so you don't particular reach out to that particular person anymore and the friendship, at least in your own mind, lapses.

I am friends with my husband ex-wife She and I, being woman, can often discuss certain things together better than she and my husband (she considers me a friend, I respond to her readily but don't necessarily ask her for anything in return; I am friends with her much like my husband is, because she is the mother of his children and "family". I am sure, too, if I needed her help with something she would do her best to help me. We remain friends because of our proximity as members of the same family and our attending some of the same family events and my outreach to her (I hold "Mother's Day" every year; she and her boyfriend come as well as sometimes her sister and sister's boyfriend and her late-80-something year old mother!).

You can only live your life so, by all means go off into it and make some space if that is what you feel you want and need! It may or may not affect the friendship but you are not here to be his sidekick friend when/if he has trouble with his new girlfriend or whatever.