90% is a threshold for a maxxed out card which is an additional FICO penalty.
+1 on the paydown. Utilization can be a real score killer. You want the number of cards with a balance to be 1, preferably your highest limit card. And you want that balance to be between 3 to 9 percent of your total credit limits across all cards.
This nifty graph from another board shows the effect of utilization across a bunch of different profiles.
If you're at 610, and fix your utilization issues, you should see a sizeable boost.
But I assume there are also derogatories or something else going on, and utilization alone won't do it.
Utilization and payment history are each around 1/3 of the total score.