Capacitor == condensor.* Condensor was the old radio term, and it's always been used on engine ignitions for some reason.
The question is, is the damage to the contacts happening when the contacts close or when they open.* When they first close, there's a really high current surge that may exceed what the points are rated for.* When they open, you basically have the motor acting briefly as a generator as it spins down, and the power that it generates creates an arc.
Your points are welding shut, which sounds a bit more like the overcurrent scenario when they close.* But it is possible that they're getting hot enough to melt from the disconnect arc, and then weld when they close again.
The capacitor/condensor will help IF the damage is occurring when the contacts open - it acts like a hydraulic accumulator and briefly stores the power generated by the motor, keeping an arc from being drawn as the points try to separate.
Unfortunately, if the problem is overcurrent when they close, the capacitor will make the problem worse.* Now you not only are trying to start up the motor, but you have even more current coming from the discharging capacitor.
Can you look at the points as they open and close and see if you're getting an arc when they open?* If so, try the capacitor and see if there's any difference.
You can also make use of the dual contacts on a new pressure switch if you end up with another Square D.* If the problem seems to be when the contacts close, hook them in parallel; now you have twice the current capacity.* If it seems to be when they open, hook them in series; this will shorten the duration of the arc.
You might also want to think about adding a small accumulator or expansion tank to your water system.* This will help smooth out the pulses and keep the contacts from chattering so many times.