I switched to a paid domain in the last few months and regret not doing it sooner - it just works, and it's nice knowing that I won't have to reconfigure all my stuff to point at a different domain name again in the future. Price was maybe $15/year on porkbun - very much worth it imo.
I've also used freedns in the past and had no complaints about them, except that I think wildcard subdomains are limited to paid supporters (very cheap though) and at the time my SWAG docker image maybe didn't support them? It's been a while. The service was great though. Never had problems like I did with duckdns.
I don't know about that - I had my roof replaced (by insurance thankfully) about a year ago, and it was ~26k. HVAC out of pocket a couple years ago was about 15k. Not fun!