Until when is it okay for a parent to help with things like dressing and eating?

There's no set age for "until when"; the guide is "how much the child can do themselves." Rather than the two extremes of helping with everything or making them do everything, the basic approach is to break the process into steps and leave the parts they can do, helping only with the hard parts. As their range widens, drop one bit of help—and repeat. On busy mornings help more, on relaxed days let them try; adjusting by situation is fine. Avoid both over-helping and pushing them away, and build up small successes.