OnlyMedication:

Fellow JAX guy here. I PM'd you my phone contact if you'd like more info.
We've done BVI 6-times from JAX. Though last BVI trip was 2016, so I'm not too current other than reading here on TTOL periodically.

Typically from JAX, your only option is Delta, American or Jet Blue to STT or SJU. We've always opted for SJU and flew SJU/EIS, sometimes with an overnight in SJU or one night in Road Town. Personally, I don't think driving to Orlando, possible overnights there, parking, returning and then a late drive from MCO-JAX, etc. is worth the hassle.

We just returned Friday from a 10-day Windwards Trip, o/way St. Lucia to Grenada. Wonderful sailing! Great water, beaches, restaurants, etc. I'll post more on that later.
We're thinking of returning to BVI but have greatly enjoyed sailing Greece, Croatia, Italy, and now Windwards since our last BVI trip. It is big world out there!

TWT - I wouldn't fly Spirit on a free ticket. YMMV