Doubling down on soft 21

Illustrious 18 states:

Split 10s vs 5 at TC 5
Split 10s vs 6 at TC 4

My 1st question is, you receive an ace on your first split; do you double down or stand?

2nd question, do you continue to split if you receive 10 cards as long as the TC dictates to?

I haven't gotten the nerve to do this split and would only do it heads up... I feel like I get enough heat as is and this would only add to it...

I also can't stand doubling 10 vs dealer's Ace or 10 at TC of 4 but have done this... It just stresses me out when I do... lol