You can split them up, but then a single marker can't move them all at once. Piggybacked artillery fire is too dangerous. I suggest allowing infantry to fire in artillery fire phase or infantry fire phase, but NOT both. Thus, you can fire before or after you move, but only once per activation. This way, at least, you can fire simultaneously with your piggybacked artillery, regardless of the results of return fire.
Cavalry can retreat all the time automatically.
OCC draws are a fixed number not taking into account reinforcements and casualties. They also seem too random. I suggest that OCC draws should be a percentage of the current force, not some absolute number. Also, the variance should be decreased somewhat, so the command advantage of one side is more recognizable. ZOC should fix most of this.