If you've been doing BLW then probably YES. If you are doing the 4 day wait rule (BLW or not) then I guess it's up to your comfort. Ophelia gets spaghetti sauce, a touch of brown gravy, curry sauce, etc... so I wouldn't worry about it IMO.
Depends on what sauce you are talking about but pretty much anything is ok for a baby. Meatballs are one of the best foods to feed babies and toddlers. You can hide tons of veggies and flaxseed meal in them.
Re: meatballs?