I agree with the other comments and answers that call out that the components you've identified seem dodgy and that you could be using off-the-shelf parts.
That said, I agree with the general idea of what you're trying to do and I have built a similar system in my shop; let me describe it for you.
First off, the shop outlets and the shop lights are on separate circuits. This is important. If a power tool blows the outlet breaker I want the lights on while I'm holding a spinning, overheated, probably electrically faulty power tool. The table saw is also on a dedicated circuit.
The circuit has a 20 amp breaker, which protects against overcurrent situations that could set the house on fire.
Second, the shop outlets are all downstream of a GFCI. In retrospect this might not have been a great idea. The shop is not damp, and induction motors can in theory change the current on the neutral when starting up and shutting down -- remember, induction is proportional to the rate of change of current, and current changes rapidly when the tool switch goes on or off -- enough to trip the GFCI. In practice I've never had any problems with it, but the GFCI in my garage -- which has a thickness planer plugged into it -- trips occasionally.
The GFCI protects against ground faults that could electrocute a person.
Third, I have custom wired the following arrangement. An armored cable with an outlet end goes from a GFCI-protected outlet to a metal handy box with one of these:
This switch has a number of interesting safety properties. It is rated to very high currents. The paddle makes it very easy to turn the switch off. And most important: if the power fails -- because the GFCI trips, because the breaker trips, or because the power to the whole house fails -- then it automatically fails to the off mode.
The dangerous scenario that this mitigates is: suppose the power fails while you are in the shop. Now you are standing in a dark room with a spinning power tool, which is already bad. Suppose you manage to safely put the tool down in the dark just as the power comes back on. Now you have a spinning power tool on your bench in front of you, cutting into who knows what and possibly kicking back towards you.
Since the switch automatically goes to the off mode in the event of a power failure, this scenario doesn't happen. The power fails, and even if the tool is still on, the switch is now off. Therefore the switch should be downstream of everything that can cut the power by accident. It should be downstream of all the breakers and GFCIs and whatnot.
That switch then powers an outlet -- also in a metal handy box -- which I have a chop saw and dust collector plugged into. When the switch is on, the dust collector turns on automatically -- I leave it switched on all the time -- and the saw is powered. I never leave the saw powered by accident because the dust collector would still be running, and I cannot run the saw without running the dust collector.
As for your 15 amp breaker, I wouldn't bother with it. Replace the 20 amp breaker at the panel with a 15 amp breaker if you're paranoid about overcurrent situations. If you do want yet another breaker, again, put it upstream of the safety switch. If the breaker trips then you want the switch to fail to the safe mode. And again, build everything out of off-the-shelf-parts designed to fit into metal handy boxes.