tjr

Take a look at Pine64 Quartz64 boards as a decent alternative

You’re best off using the PROXY protocol assuming your application(s) support it.

Unless you are committed to it, it isn’t worth it, I personally run my own but I have ran it for awhile and my IP seems to have good reputation but it is fairly difficult to get delivery to all major providers on a lot of IP addresses.

You’re probably better off using email hosting unless you are committed to deal with the headache.

This is completely standard for residential ISPs at least in the US. Your options are to either host this elsewhere or use a smarthost (somewhat of a proxy) for outbound mail.