Install a decorative stone border or edging that will help hold the mulch in place.
Warm soappy water! Cleaning products takes away your granite sealer.
We use and reccommend TS&G Disinfectant & Cleaner. It is made by MIRACLE Sealants Company and you can use it safely on Tile, Stone, & Grout. It kills Molds & Mildew, Disinfects, Bacterial, Fungicidal, Cleanses, Deoderizes, & Eliminates Oders.
You night try Pine straw instead of wood mulch. It's less prone to washing.
DuraShield by StreetBond, which is a Quest Construction Building product will solve your issue with driveway cracks. This product will need to be applied every 5yrs or so, depending on the weather conditions in your area.
Patrick McDonald
LaGrange,GA
I am sure that some work better than others. But I think it may be a drainage issue. I would check to see if you have good drainage off the driveay. and, I would recommend that you do the resealing often.
Philip
Berkeley Ca