Is Ivermectin safe for a nursing does kits? I have never used it. Probably would be wise to have some on hand.
Unless the infestation is acute and the doe is suffering profoundly, I'd probably skip the ivermectin till the kits are no longer nursing. The only real risk that I've ever heard of with ivermectin is overdose-related. Since it would be hard to predict how much exposure the tiny kits would get to the drug, it seems to me that it would present at least some sort of risk to them. If you're really concerned about the doe, wean the kits as soon as they can make it on their own (3.5-4wks).
From what I understand, ivermectin works by propping open the cellular channels that allow the exchange of chemical signals in nerve and muscle cells, resulting in paralysis and death. Invertebrates are more sensitive to ivermectin than mammals, but the drug acts on the same receptors in mammalian cells. Thus a high enough dosage can produce paralysis, possibly to the point of death, in mammals as well as invertebrates.
If the doe ends up suffering so badly that you're worried about losing her, the kits probably won't make it anyway... In that case I'd take the kits away from her and foster or hand-feed them. Then you can use the ivermectin. But I've never heard of a fur mite case that bad. Going with the oil for a while will at least suppress the mites' reproduction. If they hang in there in spite of your efforts, you can always use ivermectin after the kits are weaned.
Here are a couple of publications concerning ivermectin use in rabbits (for ear mites)
https://pubmed.ncbi.nlm.nih.gov/2329086/Eradication of ear mites from naturally infested conventional research rabbits using ivermectin - PubMed
I do feed BOSS/oats to my buns. About a tablespoon per day. My pregnant/nursing does also get a tablespoon of Manna. I don't think it's too much. ?
The majority of the Vitamin E came from the wheat germ oil in the mix we used when we discovered the deficiency; rabbits don't seem to enjoy wheat germ oil's taste so we mixed it with things they
did like. What you're feeding wouldn't cause me any concern. I think too much E is related to blood thinning issues; too little seems to depress reproduction - lack of interest in bucks and does, missed pregnancies, dead or dying kits at kindling, poor mothering behaviors, and interestingly, ears that flopped over at the tips in entire litters of Satins. That last one was the clue that helped me and another breeder figure out what was going on after
16 months of virtually no living bunnies being born!