Floating IP's are not the same as the dedicated IP you get from the VM itself. I've been sending outbound on that for the better part of 2 years.

To the other point, if you have a problem with spam scores, you are probably sending too much mail for this sort of solution (consider Mailgun 10,000 emails/month for free). For an individual it is fine, not for use as a mailing list. A clean IP address (every IP I've ever tried was clean), DKIM, and SPF will allow you to hit pretty much anybody. It might take a few people pulling you out of spam on gmail before you can send to them, but I think that's true of any new mailserver.