So I'm going to approach this in two ways - as if your husband has it, and if he doesn't.
If he already has it, nothing changes for you. If you have outbreaks on your butt, and it doesn't physically hurt you to have sex during outbreaks, then go for it.
If he doesn't have it, having sex during an outbreak increases the chances that he'll get it, even if your outbreak is on your butt. Since your infection is genital that presents with outbreaks on your butt, you will shed the virus from your genitals. You shed more during an outbreak.
Apparently, your husband doesn't care. He thinks he has it, and he might. He might not.
If he doesn't have it, and gets it, nothing will change.
If he doesn't have it, and all you do is avoid sex when you have symptoms, the chances that he'd get it from you are about 4% a year. If you take daily antivirals to help reduce shedding and outbreaks OR use condoms, it's 2% a year. If you do both, it's 1%.
As to the spreading, you could get an outbreak in the genital area at any time. It's common to continue to get them in the same place, but that could change, too.
You should read the Herpes Handbook at https://westoverheights.com/herpes/the-updated-herpes-handbook/ It's free, and written by Terri Warren, one of the world's leading experts on herpes. You can read it on any device.
I'd also urge you to remember that your husband is a grown man who can make his own decisions regarding his health. If he's good with it, you might want to follow his lead on that. I don't know him, obviously, but on this at least, he sounds like a great guy.