Fingernail can scratch cooking board = too soft? I was using a lot of elbow grease to sand down my cheap cutting board to remove the deep grooves caused by my knife. Then I questioned myself if it's even worth the effort and just get a new better quality cutting board. I recently realized can scratch my cutting board with just my fingernail. Is that sign that it's too soft?

American Test Kitchen recommends the Proteak cutting board because it's not too hard or soft. I will get this board if it's truly worth the money.
Since it's not all that clear what your question really is, I'm going to go with the question in the title:

If you can mark your dry cutting board with a fingernail, the wood is softer than you want for a good cutting board.  In fact, your cutting board would need to be a very soft pine, fir, or similar wood to be that soft, none of which are ideal for cutting boards.  This explains why you have "deep grooves".

I own a teak cutting board (it was a gift), and I don't know that I'd recommend it.  Teak is hard enough to dull my knives faster than a softer hardwood like beech or maple would (bamboo has the same issue).  Beyond that, there is quite a bit of debate about which wood is best for cutting boards and instead of trying to reproduce it here I'm going to give you some reading:


Tasty Kitchn's Best Wood for Cutting Boards
Serious Eats Recommendations on Cutting Boards
Brooklyn Butcher Block's opinion on various woods