Many combo type products only have Biotin in micrograms in them.

I think you need MILLIGRAMS for a while. It takes many weeks to fix nails, as they grow slowly.

5-10 milligrams a day would be your target.

Nail health is also dependent on good thyroid levels. Since the MVT affects iodide absorption as well, you could be having low thyroid functions.

I'd stop the lipoic acid for a while and see if things improve.
Ask your doctor for an evaluation of your thyroid status too.
There are some warnings about high dose lipoic acid affecting the thyroid.

This is an example from Amazon:
Amazon.com: Natrol Biotin 1, mcg Maximum Strength Tablets, 1-Count: Health & Personal Care

Biotin purchased locally in stores may be more expensive.
I get mine at Puritan's Pride.

If you have any burning mouth or other mucus membrane areas the biotin can help that too. (mostly female areas).