That's sweet, and I suppose "Cub Daddy" is better than "Club Daddy."
But seriously, whatever works for 2 guys, that they both enjoy, I think is good. I'm quite sure it brings them closer together, as a sign of affection.
I don't know too many of our friends (in our older demographic) who use nicknames except when alone, so semantically it's more a private endearment than a regular nickname. I generally just say "my love" when talking with my partner, as in "Good morning, my love" (like this morning), or "I'm home, my love!" and so forth.
Now my partner did start to call me "Junior" in public when we first got together almost 3 years ago, which I didn't like at all. I was in my late 50s, not anybody's "junior," which I've always taken to mean a dismissive term for kids and sometimes adults. But worse in his case, it's also the name of his dead dog that he adored, whose painted portrait is all over the house, and his gay friends all know that. No thanks!
Well, we talked about that and he stopped. Now in public he just uses my ordinary nickname Bob, but in private a few little endearments I can't bring myself to type here (and no, not pornographic). These things are good, although I'm not a fan of the more saccharine and cutesy ones.
I'm reminded of the old "Mary Tyler Moore Show" TV sitcom (gawd, going on 40 years ago!), when her gruff TV producer boss "Lou Grant" barked to sweet little Mary while she was trying to cajole him:
"Don't be cute, Mary! I hate cute!"