Really you're best off on a 150 Nug, but the Directional 152 is the second go to. it wont feel the same going backwards, but really the only boards that you just should try to stay away from switch are those like the Fish, or swallowtails.
I have not ridden it, but the idea of the Harvest might be the dumbest thing I've seen. To make the Nug work and allow to downsize 10cm you need everything the Nug has. Deep sidecut, blown contact pts, rocker, squeezebox, and midwide waist. Throwing full camber into that just makes no sense to me at all.
The Twin was a mid stiff board with a fair amount of Camber though. You'd be much more comfortable on any good mid stiff park deck around 157-159. You'll progress fine and as you get better the board wont hold you back.
As far as foot pain, that's likely boots.
Go ahead, drink that kool-aid.
FS: Forum Sauce 142 $200 plus shipping
FS: Flux SE30 $75 plus shipping