I'd assume you'd have a LOT more issues with the wetsuit than with the BCD. Did you have to get a custom-sized wetsuit? I'd expect an XL or XXL BCD should fit you fine.. just walk into any store and try some on. Most rental places will have those available.
No vacation rental place that I'm aware of will rent a BP/W. Maybe a tech diving store will. But personally I wouldn't suggest you learn how to dive in a BP/W. (Using those requires you adjust all the sizing correctly, and add trim weights appropriately. They're excellent for when you know how to dive, but only if your instructor uses one and knows how to adjust it for you....). Learn to dive with standard gear you can rent anywhere. Then you can worry about changing stuff to make your dives better....
Basically, there are two big measurements that will matter: length from shoulder to hip, and waist size. Your weight is completely irrelevant. Thankfully, most BCDs are highly adjustable, which is why I suspect the XL or XXL would fit.
Just remember if you're wearing a thick wetsuit, your waist/chest is gonna be even bigger...
If you are ever in Key Largo, we, at Silent World, rent Halcyon back plate and wings!
Pat