The only problem with using a urethane adhesive/sealant (I assume Aquasure is similar to Aquaseal by McNett?) is that it will be near-impossible to remove when you have to replace the seal again. I would look at using some heat activated seam tape (a lot less adhesive, and not as goopy as hand applied), or use the neoprene cement as a final coat (dust with talc to keep it from gluing itself together.) A good glue joint shouldn't really need any kind of exterior sealant.
Fishing line (monofilament) would be OK for stitching, especially if covered; it can, however, be rather abrasive on skin if it's in direct contact. Regular Nylon thread should be fine for stitching (that's what the wetsuit manufacturers use.)
Paul: the seal-to-suit seam should be far enough up that it will have no effect on suit-to-wrist sealing. Sealing will take place further down the seal's taper.