[Jack]

would tend to err on the heavier side instead of lighter if I was needing a wetsuit.
Advice-wise, I would go with a good-fitting 5 mil, and take the vest with. If you're doing multi-days, or a liveaboard, that could come in handy.
A 7-mil in 70-ish water would probably be a little TOO heavy, especially if you're good in a 3/2 in 71 degree water.
The hood will really help a lot, BTW. Wear boots and gloves, and you will be comfy, I think.