This isn't Toronto or Montreal. This is a HORRIBLE day for walking and you're on crutches. I'd advise taking the bus or hailing a taxi.

If you insist on walking, I can reduce the # of blocks outside to 4 blocks. Walk those 4 blocks to 5th & 42nd, descend to the subway (this involves steps—be careful!) and walk underground to 6th Ave, hop on the B, D, F, or V uptown 1 stop to 50th and 6th. You don't need to use steps to go outside. There are escalators depending upon where you're going.