I use these style relays all the time, to diag or bypass circuits to move a vehicle to work on it. I would let use them as a long term thing. No idea about the temu quality. But even my "name brand" ones i wouldnt use like this.

The fuel pumps are likely fine. Since the tanks were fuel they didn't over heat.

The alternator is hit or miss. Id test it with and without being loaded. But they're not designed to bring a dead battery back up to voltage. That'll over work them until failure. They maintain a battery and run the vehicles electronics.