Hi John (Dear John sounds too much like a brush-off!)
Not having much luck to date, are you.
I'll give you some ideas ,though they're not definitive and might be poo-poo'd by others.
MOTOR: Torpedo 400 (direct drive). For extra torque eg. to turn a slow revving four bladed prop, try a geared Torpedo 500 though you'll need to have a deft touch with the Go-Go stick in order to maintain a scale like speed - snail-like in the case of the Puffer. However it's better to have speed in hand to get out of trouble which is a feature you'll get from the '500' which may be otherwise slightly overpowered for this particular model.
ESC: Try MTronic - the smallest will suffice for the '400' motor though you'd have to check out the desirability of having a higher rating ESC for the '500'
BATTERY: Suggest 12 volt sealed Gell Cell battery of between 4 and 7amh - it'll provide duration on the water and also much needed internal ballast.
BACK ISSUES; sorry can't help you there .
If you haven't already done so, pop along to your local model boat club. Members are always willing ,if not eager, to give advise and may also be able to offer practical help at the workbench.
Good luck and may the revs be with you.