If your UTL is almost 90%, any card you will get approved for will not be worth it to transfer a balance to!
Having an AU does factor in and count towards your UTL. The only problem is that some credit analysts will see that, and if they're good at what they do, or they're just mean, they won't count it. A computer on the other hand will! So if you apply online and get approved instantly, a credit analyst never looks at it.. (just a thought)
I would recommend that you pay down as much as you can, let it report, and then apply for a balance transfer card. Citi has some good ones.. and I know I saw BoA has one also.
What you could do for now, if you haven't angered Discover is call them and ask for a CLI. Tell the rep that you know you're near your limit, but that is exactly why you want to have an increase. Tell them you are very vigilant about your credit and you understand the need to have available credit reporting to have a decent score. Also tell them that you were simply taking advantage of the 0% interest with them and don't want to move your balance if you don't have to.
If they mention the lack of tradelines you have on your CR, simply tell them you don't like to live beyond your means, and that Discover is more than enough for you.
If that doesn't work.. there's no harm in asking if they can lower your APR or can extend your 0%...
Other than that.. I would say pay it down as much as you can regardless!
I recently was approved for a Citi card (in July) that has 12 months 0% interest. Then, in changing around accounts @ US Bank, applied for a VISA (to avoid charges on checking account) that is 0% for 12 months, then got an invitation to apply for MasterCard @ 0% for 20 months. I got off the phone with them after I applied via phone for the 12 months 0% and logged into my account. I had a message in my message center about the 20 months 0% offer. I applied and was approved for both. Quite surprised, but both approvals allowed me to move all my oustanding debt (except mortgage) to 0% interest. I have budgeted it all out and will be debt free in Nov. 2014! hard to believe! Life has thrown me a lot of curves (job loss, medical debt, huge house repairs) but somehow, I've survived. Many thanks to everyone here...stay on these boards (all of them) and you will learn so much and get inspired to stay on track. good luck!