Thats a good time for your half marathon, Well Done!
I found that my toes went numb with new trainers too, I tried tying them a different way. I was tying them @normally@ only going through top hole and tying in a bow.
I tried; going out of the 2nd hole then in the top hole, kind of adding a bite to the lace. then tied in the normal way, in front of the tongue. The bite in the lace takes the strain, and the bow just uses up the lace, so it's not flapping round.
Ive done this with both my running shoes, and it seems to have worked.
I hope it works for you.
Got another half marathon on sunday. anyone doing Eastbourne half?