The "crabwalk' strafing is an artifact of animating in the BF2 engine. Not too much can be done with that without serious animators to work for the mod, and even then might not be able to stop it.
As for stamina, FH2 USED to have stamina, and it was a pain in the ass for all when you'd be trying to run from cover to cover but would suddenly, magically slow down as if your life suddenly didn't matter all that much, or would get hung up on a little rock or box and be unable to jump over it, or, if able to jump an obstacle, would be unable to run after it. It was not a very good, realistic, fluid combat situation. Yeah, running is tiring irl, but know what else sucks? Being shot. If a soldier has to run, they run regardless of how tired they are, and definitely do not randomly slow down in the middle of running to cover.