How realistic is it to be able to do all this from a Digital Ocean or other VPS, given that those IP blocks may have already been used by spammers or may be used periodically by spammers? I.e. it's trivial for them to set up VPSes on the fly.

I'd feel nervous about doing this at home. For one thing, my ISP is a residential cable internet provider, and not 100% guaranteed uptime as a result. I'd hate to miss mail or worry whether I did.