I am destroying my fingernail with my old timey playing. Help!
 

So I play a style of guitar known as "Carter scratch," named after Maybelle Carter's picking in the late 1920s and early 1930s on Carter Family records. I play old timey Appalachian ballads mainly, both those that were originally for guitar and I've converted some banjo songs into guitar songs, and I've been told the way I play is very banjo-esque. Basically I pick the melody on the lower strings with my thumb (usually thumbpick), and "scratch" the higher strings to make the chord by flicking my index finger out and kind of scratching it back toward me to get both a down and up rhythm.

I play fairly aggressively, and recently I've started to F my index fingernail up. First the end of the fingernail started pulling away from the fleshy part underneath, so I played less for awhile or used my middle finger (not nearly as easy as index). Then I started back with the index, and now the fingernail has a small tear just behind where it goes from white to pink; it's not all the way through and only hurts when I try to play, but it's a bit worrying to say the least.

Does anyone know of a pick or some way to protect the fingernail that would still allow me to play this way? All other fingerpicks I've seen or tried are made for "one-way" picking, i.e. it would get hung on a string if I tried to do the back and forth scratching (like these, or these). I eat quite healthy with quite a bit of calcium, not sure if I can really improve diet-wise. Any ideas??

An Alaska pic works for me. Downstrokes and upstrokes both. It stays put for me but some folks keep it in place by using a disposable glue dot on top of the nail or wrapping tape around the pick and finger.

I had acrylic nails for a while that also worked well but I moved into a rural area far away from the nearest nail salon.

Interesting. Maybe I'm showing how little I know about actual fingerpicking, but you can go to a regular nail salon and have an acrylic nail put on for guitar playing? Is it a pretty standard transparent nail, or do you have to ask for anything in particular?

Yes it's nothing out of the ordinary ... ask for an acrylic nail for guitar playing.
It's a bit unusual for them to do just one nail but they'll do it I'm sure.

It's looks a bit different than a regular fingernail and will stand out a little bit more if you're getting just one, but you can try it once to see if you like it.
It's something that you'd need to get touched up every three weeks or so.

I think if you have a close look at Mother Maybelle's 'scratch' style playing you'll notice that she:
- wore a thumbpick like you
- wore a steel fingerpick on her index finger, for up-picking
- and "stirred" (down-strummed) with her other fingernails
Maybe she wore out her fingernail too :)

Do be aware that if you remove the synthetic nail, your natural nail will likely be very weak and thin underneath it. At least, that has been my experience. If you want the natural nail to heal, you may not want to choose that option.