Sandy soil has very little nutritional value and dries quickly. Add lots of composted manure to the soil and I’d also get a bag of Espoma Tomato-Tone food. and be generous with that (according to the label of course). You say that the tomatoes “have grown very very tall and spindly with few tomatoes”. This is usually the result of trying to grow tomatoes without enough sun. Tomatoes need 8 hours of direct sun per day MINIMUM. 10 or 12 hours is even better. Perhaps you need to grow your tomatoes in a sunnier location?