You say you have nothing reporting on your credit file in the last paragraph, but you say that you're disputing several items and inquiries in the opening paragraph. What items are you disputing? Why dispute inquiries? If they're legit, this can only come back and cause problems for you (fraud alerts, etc).
The accts you're talking about applying for are not going to help you at all. You're far better off following your brother's advice of getting a 1-2 secured cards (w/ issuers who graduate automatically in less than 12 months) and put up the biggest deposit you can. Adding a few AUs would help as well if this is an option.
How long did you have the auto loan for? Had it not already reported before you paid if off. I don't know that you'll get a big score boost by having a paid installment loan report.