Today I exchanged a few emails with the vet at the extension. Evidently disposal of the animal is included, but that's just tossing out in the landfill (admittedly, I have no problem with this, even though that probably makes me a heartless pet owner). If I chose to incinerate, it was an extra charge. When I mentioned that I didn't see landfill as an option, and why I chose it, she said she would reverse that charge, which I thought was very decent of her. I also thought it was very kind of her to answer my questions about my flock. I've been losing sleep over what I could be facing, and she helped put my mind at ease.
Essentially, LL is incredibly common in the chicken community. She used the term ubiquitous, which is such a lovely word, and not used frequently enough. Ubiquitous means that it's found everywhere- more than 90% of chickens have been exposed to it. She said that the only way to guarantee a flock is LL free is to have each chicken tested before having them join the group, and to be prepared for a lot of positives. Having them actually get the tumors and die is fairly rare. If a flock starts having a lot of losses, it's probably a good idea to cull the rest, but odds are, it won't go that route.
My plan is to keep the remaining six chickens separate for a few more months. If nobody else gets sick, I can basically relax. Yes, they are all exposed, but it sounds like it isn't that big of a deal most of the time.
I also have great news! My cream legbar is officially laying! I was pretty sure that she laid an egg yesterday. My lavender ameraucana eggs have had a particular shape to them (almost pear shaped), and always have some little calcium deposits, called "pimples" on the narrow end, and have a greenish tint. The egg I got yesterday was smoother, more oval shape, no pimples and appeared more blue. Today, I got one of each, so I have my answer!