use a cast iron or a pot that is solidly built with thick walls.
don't forget you are melting an alloy in this pot at a temp of over 600F . some really cheaply made pots can actually cave in on themselves at high temp and heavy weight
be safe and work in a clutter free area, think safety and plan ahead of how you are going to work. if you have to use a thin walled pot, melt small amounts at a time.
as for the leak in a lee pot, there are ways to resolve that. I would suggest first to empty the Lee pot completely of lead and have a close look at the mechanism from the inside at the bottom, take it apart, clean it.
you might find all sort of sand and dirt stuck in the spout which prevents it from sealing properly. second i would suggest to use some very fine valve lapping compound to smoothen the surface and remove any burs. lap the two parts against each other carefully , small steps at a time until good contact is formed between the parts.
stop frequently and check the seal, don't over do it.
put it back together, put a bit of water in the pot and check for leaks, if done correctly there shouldent be any
if there is still a constant drip try to pin point where the leak is coming from. much easier to work with bit of cold water than molten lead in the pot.
i found out that adding some weight to the lift rod helps to keep it pushed down in place so i put a few heavy washers on the pot handle which keep it weighed down.
see if any of the leak prevention methods from the lee pot work for your applications.
hope this info helps.