Can you use marinade twice if it was first used on precooked meat?
The general rule is that if the food has not been exposed to potentially dangerous temperatures (40 - 140 F, 4 - 60 C) for more than 4 hours cumulative over its lifetime them it is safe to use.  This would apply to your sauce, so if it was hot the entire time it was being used, it should be okay.

If your marinade meets that constraint, then you might consider reusing it.  However, it will have been diluted and infused by the meatball flavors, so the result may be strange or it may be fantastic, depending on how those flavors interact.

Given that ribs are not inexpensive items, I would start with a new "marinade" sauce, so that you have consistent and predictable results.

See also: https://cooking.stackexchange.com/tags/food-safety/info