RE Load Limbo & Per Diem

Two unrelated questions:

1_) Very, very often I get stuck in limbo between loads - that is, I've sent in my empty at final and it's been accepted, but no load info has arrived for the preassignment. I send a mac11 asking for the load info, but often times it goes unanswered for hours. Am I able to just start driving towards my next pick up and accept the load info en route, or do I need to park and wait until they get around to sending it to me?

2_) I see a lot of people saying that I shouldn't do per diem and rarely, if ever, an explanation as to why. Could someone explain?

3_) (BONUS) In regards to #1, why is it so hard to get dispatch/fleet to respond when you need help? I spend so much time waiting for direction, and when I call I get someone being rude to me. Called in the other day asking for load info and the guy on the other end told me that if people stopped calling him, maybe he could get things going. He then said to another dispatcher, "I just want to hang up!" and then he did. Really professional.