Dont know what your expectations are but you are better off heading inland . Where are you coming from and what do you ride? Sorry , but have lived in those Towns and there is no pleasure in riding there .
Unfortunatly Sheppeyscum.com no longer exists. It was one of the funniest websites ever. I know the area well as Jackie’s family moved there after she left home. I suspect the pub you refer to is the The Ferry House Inn at Harty. I wouldn’t take a car down that road, never mind a bike. The road has always been sunken, bumpy, cracked potholled and sh1t.
Head towards maidstone on the A249 from the island. From Maidstone town centre head south(ish) past the police HQ on the A229 towards Hastings. Follow it towards Tenterden and Biddenden. Take the A28 (I think) towards Ashford. When it gets to Ashford follow towards Faversham (A251 - this is the best road). From Faversham take the A2 back towards Sittingbourne and then back to the island. Takes no more than 3 hours if you stop on route and is learner friendly but still fun if you are more experienced.