My 2.5 yr old supposedly has toddler diarrhea. Because of his issue I can't get him fully potty trained. When does "toddler diarrhea" usually clear up?

Patience. About 25% of kits train at 2 yr, 75% at 3yr and 90 % at 4.If your kids not ready the diarrhea issue will not matter. Try to let the kid rehearse, provide easy access to the equipment and let him know you will help when he feels the need. It will happen when and if he decided it's time.
Yes. I know toddlers diarrhea can be very frustrating for the family and the child. However it does typically clear up without any problems. It just takes time. Hang in there and keep working on potty training.