Re: multiple hands
Technically, since you are playing two hands at once, you can spread to two hands of $35 each and still keep the same Risk of Ruin. The benefit of two hands is that you can safely get more money on the table than with only one hand. In general, you can safely spread to 2 hands of 73% of your original bet, or 3 hands of 57%.
On the flip side, the optimal number of hands that you play should be based on the number of players at the table. Here's what Schlesinger's BJA says:
Playing alone, stick to one hand of $50.
Playing with 1-2 other players, spread to 2x$36.
Playing with 4 other players, spread to 3x28.
And, of course, don't EVER play with more than 4 other players. Some people don't even play with 3 others.
As far as giving the dealer a worse hand, that won't be a consideration. The cards come out randomly, so you will get the low cards just as often as he does.
-Sonny-