I recently replaced the previous guild master since he hadn't log in for a month but the guild feels so dead with a lot members last login nearly 1 year ago or more, i tried to leave but dont know how.. there's a disband guild option but it gave 'another guild member exists' is there some way around this coz i can't appoint someone else since a lot of them aren't active anymore?

Click on your name. You'll see the option to leave the guild on the right. Press it and confirm you wan a leave. It will then release you. You'll have to wait two hours before you can apply f9r another guild though.