Nice report. I live in Houston also and want to take the Dual Sport out to do the High Island to Sabine Pass.
I like your plan to get to Key West on coastal roads. I had a similar route planned from Houston to St Petersburg over the Christmas and New Years holiday. Because of limited time I had to superslab a lot of that, but did get to do the sections in MS and AL. Didn't make it in time to take the Dauphin Island ferry, though.
Right after (heading east) that Ferry is the Rachel Shipwreck
that may be worth a quick visit.