Aren’t you making things more difficult then they are?
ISP->Modem->pfsense->ha
and use your domain name in pfsense
then in IOS
local: https://my.domain.url:8123
external: https://my.domain.url
I never really understood why i would need a reverse proxy (except for blocking improper pages for my younger kids )
What i did here with my router, would also work on your pfsense