99 F350 7.3 cranks but no start, tried to hit speratically

99 F350 with turbo 7.3. Truck is automatic trans, and When put into reverse,
does nothing until you hit the gas pedal and get to higher rps. Will then
gradually start moving backwards, and pick up speed. Trans fluid level is good,
and has maintained consistent. Does not do this in forward, nor does it have
any lag in shifting in forward gears. I know it's in the trans.. but, how bad is it,
Doc?

After moving reverse the first time, I shut it off, then came back to it maybe 30
min later. Wouldn't start. The way it acted seemed very much like it had air
locked in the fuel lines. After trying to start and purge air for a bit, it started.
Began kinda rough sounding, gave some gas in intervals, it eventually was able
to get high rps again and idles lot more normal..
2nd time to reverse, same issue with moving backwards. But this time when I
shut it off, it wouldn't start back up at all.
Sounds like air locked again. I've purged air, I'm getting fuel to can and prime
seems accurate.. it cranks fine, but won't start. During the crank it sounds like it
hits periodically, but won't take off still. Any suggestions? Any help is
appreciated.