Disputing Credit Report Entries -Advanced Question

I'm trying to help a friend out with his credit report(s). I remember I did this years ago with mine and I was pretty successful getting my fico score higher. Researching this stuff is actually kinda fun (yes I don't have a life right now).

Question:
1) yes i know you can dispute negative entries that are on your credit report, especially if they have no right being there but if a negative entry IS correct, should you try disputing it anyways on the off chance the creditor will not respond and it will be taken off?

2) If so and the correct item is disputed, which reasoning should be used to obtain the best percentage of removal success? Ie. Never had the account, Never late... etc etc..

3) If the negative item is showing up on all 3 credit agencies (experian, trans, equifax) should they be disputed with all 3 at the same time or one at a time?

4) At what score does it just not matter anymore. Ie. is the bank rate for a 790 score the same as a perfect 8-something score?

Thanks in advance.

 

Done. I didn't even know about the subscription stuff. Sorry about that, was wondering about the PM limit. NICE!