Definitely serialize it, why not? You really want to have a novel to your name, why not use the financial and moral support this platform allows to make it happen?

You should definitely use your current account. You have a following of people, that are in part people that want to read that novel. You have other followers that are interested in you, and want to be exposed to more of your content. I honestly can't see a reason to open another account, unless you want to have a "serious" account, for "business", which I know you don't. Either people want to work with you, as you are, or they can go look elsewhere.

I don't see an issue. People that already saw it and don't want to upvote it again, simply won't. It's not like you're just copy pasting, you're starting over with another draft.