The existing drain is almost completely full with food and grease. The mechanical snake will not open the drain. The line could be jetted but because of the large belly, unsupported pipe, and backflow I don’t recommend the jetter. I recommend repiping the drain to ensure proper drainage, be code compliant, and be less prone to clogging in the future. The line will be cut out and repiped, in the crawlspace, to give proper pitch/fall and be properly secured. Part of the laundry drain, tub drain, and bathroom sink drain will also be repiped to accommodate the new location and size of the branch drain.