Broadcaster and Telecaster rhythm pickups are not wax potted, but were treated with a potting solution to protect the coil from damage and give mechanical stability. After the coil and bobbins are potted and let dry, the cover is then put in place and the 3 tabs on the cover are mechanically bent over the edges of the Fibre board to hold it in place. Early amplifiers had low output and feedback was not as prevalent until the higher powered amps and performing in close proximity to the speaker caused the pickups to start howling.

I never like seeing an old original pickup modified or changed in any way. Potting the pickup will lower the value even though it may improve the performance of the instrument. If your wiring has been modified or the pickups have been soldered in and out, I would try to find a vintage replacement that has been specially made for your desired sound and output and one that’s properly potted to eliminate unwanted feedback. When using the original pickups I would try moving further away from the amp, or turning down and letting the monitors or PA do the work.