Have you tried Mache or Orach? What about mustard greens? Mustards for Mustard Tiger

? Regarding the seedlings being eaten I use milk/oj jugs as cloches. Cut off the bottom and leave the cap open. Ta da, instant, recyclable and cheap cloche.
Wash with soap and water anyone who is seriously infested. Borax the coop area. DE is fine. I don't use Sevin, too harmful to other things for my taste. I use Frontline. I had a long time breeder and poultry judge tell me to use it. I am so so so grateful. It worked great. A drop under each wing, between each leg and at the vent-- and if you have crested birds you should put a drop on their heads. I also find that tea tree is a helpful step in between. Lavender oil might be a gentler alternative if you have it. I had a Polish cap that was really bad off. Mites and lice at the same time. Talk about gross. Frontline from Walmart was the best deal we found. Fast intervention will save lives. Lice and mites suck the birds to bone in rapid time.