I don't actually want tell to tell you what to do or buy. I want to complement some of the technical information and good advice you were getting, particularlarly on the stepwise way to proceed. However, it is unlikely anybody else on this forum is going to promote the safe wiring practice I will go on to mention until it spectacurly bites them plus ten friends on the a**e at great expense. That needs a diagram while I have my own workshop to refit.
On the phone front, I have an Android but had to grant access to my files & photo gallery. I use the P Add image to post button after shrinking photos to a few megabytes.
It may help future replies if you briefly list rc gear and components you have available.
For example, other speed controllers, connectors, batteries.
An upcoming diagram will illustrate the safety aspect in controlling the bow thruster with a servo & microswitches. It keeps to one, and only one, connection between your drive battery (here at 12v) and the negative rail at the receiver. If you had a servo operated rheostat speed control, so much the better.
Some would champion solid state or electronic switching as reliable. The problem is an additional connection in parallel to a first creates an interference signal on top of the rc signal to speed controls. If either of the negative connections from speed controls to a common battery becomes loose or resistive, you would avoidably loose an esc.