Should be around RM220 or RM230+6% (if any) for Platinum. I'm also a Plat member; but with AIA Vitality received 30% rebate for monthly membership... so every month I'm only paying RM170 or so. You can refer to one of my AIA Vitality post in this thread - probably 1-2 pages back.
Platinum price is as per above. Not sure about single club. I'll recommend to go for Platinum for easy access to all clubs. Also refer to my AIA Vitality post 1-2 pages back - you can save a lot with this, no joke. I'm surprised to hear people still paying full membership fee when they can benefit from Vitality.

Also, FF prices are pretty much fixed. Not sure from whom you heard can nego, but sadly, it's all fixed. The nego part is likely to be waiver of registration fees, admin fees etc that you pay when enrolling in the membership. Ask for the free gifts as well (bag/ tumbler etc).

Sure you can. Show the front desk your Vitality card and ask them to do the membership adjustment fee for you. It's quite fast. In the following month you'll see the new fee reflected in your statement.

Add+:

You need to sign a new 12 months contract with them

My 12 months contract was already over when I applied for vitality status. If your existing contract was not yet expired, then only pls check with them.