Not to downplay the intent, but hosting static site is much simpler in something like github or netlify. Also in my area business internet with fixed IP is more expensive than what I would pay for decent enough cloud instance($50 vs $10).
Not to mention that most “dynamic” IPs change only while the router is offline and your lease is up. So as long you don’t power it off, it may not change for large intervals of time.
I think a design where you rent a cheap $5-$10 vps with a static IP that forwards SMTP messages both ways through a secure tunnel to your personal mail server in your home would be a good starting point for self hosting.