I don't think padded shorts will help you get over the pain of breaking your butt in. Actually, I suspect the padding aids comfort primarily by wicking sweat away from your butt.

I'd plan on shorter rides spread a day or2 apart until you can sit on the seat comfortably. Same for your hand, wrists, and arms.

Enjoy your bike. Congratulations!

BTW, as you condition yourself, you'll probably find that your HR will get lower on the same route at the same speed, or your HR will stay the same, but you'll keep going faster or farther.