I've always had issues with canned starch so I've starched my fabrics heavily using StaFlo in a dishpan and hung up to dry. Every once in awhile, I'll have to clean the bottom of my iron of excess starch after I've pressed all my fabrics though. But with the canned starch, it was a constant problem.
As to the broken top, can't give you any solutions but I understand what you're going thru. I do a lot of spray can painting and I always have an issue with this one type of paint. It's a topcoat with glitter in it and most times it will clog up after just one use and nothing I do will unclog it so I end up having to just throw it away. I've changed the nozzle hoping that would do the trick, stuck a wire down the hole to unplug it and I just get spray coming out then but not with the nozzle top on. Spray paint has gotten so expensive these days too so I just wait until I have a lot to spray using this special spray so if it clogs up on me, I've used more than just one time with it. I've only had 1 can where I was able to use the entire can of paint so far.