I think worming them is a good thing. No, just treat them that one time, wait ten days, then treat again. You are supposed to not eat any of the eggs for fourteen days after the last worming, but I only get rid of the first couple of days eggs then use the rest for personal consumption (or to cook and feed to the dog). The Safeguard is excreted mostly through their gut so doesn't stay in their system long, it's up to you, but I wouldn't sell any of the eggs for that 14 days. If they had worms (quite likely) you should see a big difference within a week or two... less feed consumption (you're not feeding all those worms!) and just happier chickens, and they'll probably lay alot better as well.
Don't worry about the "rubber" egg. Sometimes a hen's plumbing gets out of whack and they'll lay some of those soft-shelled eggs, unless it continues for a long time I wouldn't worry about it. The chickens seem to instinctually know which ones are soft-shells and immediately eat them, but that doesn't mean they will eat all eggs, just the soft-shell ones. Just make sure they're getting plenty of calcium, sometimes it will help to put a small amount of apple cider vinegar in their water to help them absorb the calcium. Remember, those poor hens had crappy living conditions for quite a while, so it will take awhile to undo that!
I don't know about any other types of wormers, hopefully dawg will jump in and help you.
Don't worry about the "rubber" egg. Sometimes a hen's plumbing gets out of whack and they'll lay some of those soft-shelled eggs, unless it continues for a long time I wouldn't worry about it. The chickens seem to instinctually know which ones are soft-shells and immediately eat them, but that doesn't mean they will eat all eggs, just the soft-shell ones. Just make sure they're getting plenty of calcium, sometimes it will help to put a small amount of apple cider vinegar in their water to help them absorb the calcium. Remember, those poor hens had crappy living conditions for quite a while, so it will take awhile to undo that!
I don't know about any other types of wormers, hopefully dawg will jump in and help you.