I wouldn't do a payment plan without strict guidelines if a payment is missed. For example, any payment more than 15 days overdue results in her losing all equity in the properties and they go to you. Otherwise, you have no teeth to collect and it will cost a fortune trying to. It's most wise to cut all financial ties by whatever means necessary. If she is unable to buy you out now, a court would order one or more properties sold to satisfy the debt. This also gets complicated and must be carefully worded so at to actually force the sale, in how much time, with what's a reasonable offer, etc.
The tax directed stuff is very complicated. You would need an expert for direction. The laws vary greatly from state to state. Your case is not simple enough to not have an attorney, unless the eventual outcome of giving away the properties is acceptable to you.