Front Suspension problems of the 1999 Nissan Quest

Purchased 1999 Quest and went back to seller about vibration and he(reid melton) said that it was fix a flat. We found out that there have not been any fix a flat put into none of the wheels. Front end have been aligned by us a total of 3 times. Beam Nissan have worked on the front end and exchanging out other part 10 times. It is better but it still vibrates. Nissan dts said it is comparable to other Quest. The new tires that we had put on is wearing out on the outside. One of the alignment shops that wer took it to thought that we had a set of bad tires, so we put this new set on. Beam Nissan have had it at an alignment shop for 3 times. This vehicles vibrates at 58-63 mph and the seats just rattles and is very noisy while driving. You can feel the vibrations at other speed but it is the most noticable at 58-63 mph. We are afraid, because we don't know what will happern while driving this van. We are embrassed to ride others. We have been to bbb, but they denied the repurchase because of the local inspector. They telephoned him about his decision. He did not read his notes from coast-coast inspections and took us for a test ride and made comments to us that was not in line wiht the faxed report that we received. He said that he (herby james, watkins auto sales. He did not tell them what was on the inspection report. They had interpeted his comments. I have all notes and paper work and a signed letter from beams service manager about them not being able to repair my vehicle. I have contacted the attorney generals office. They told me to contact this office. This van had only 22,314 miles at the time of purchase with a full warranty. By the dts for Nissan saying that it was comparable I can no longer get the repairs done under my full warranty. We feel that this van is unsafe because they have admitted that they could not repair the problem. We have been told that we may have to put up with the vibration that we may just have a bad one. Please help us.