Tough to say. Depending on the time of year I've heard anywhere from $100-$120/night being the general average.
The big trick with Ebay is to pay attention to the seller's ratings, and to make sure those seller ratings are for timeshare transactions. (just because they have a perfect rating selling little $10 trinkets doesn't mean they will be reliable for a big ticket vacation rental). You can also often contact the sellers directly to try and work out something for your exact dates.
There are several bigger renters who use Ebay for the advertising and transaction capabilities of the site, but who will work with you outside of the site to arrange your vacation.
For a 3bdrm I'd honestly start sooner rather than later. We are now in the regular open reservation window, so there is no reason to not start looking around now for your reservation for next year.
Because of the lower number of 3bdrm units at the resort, If you really need a 3bdrm I feel it's better to try and find something now that you are happy with, then to wait in the hope of a better deal and discover that all the 3bdrms are booked.
Because of the way the points are used when making a reservation, and the way the larger renters manage their inventories, You are not as likely to see the prices drop if you wait it out. Most of the really great last minute deals are when an owner has points or a reservation they have to use or lose, and that time of year you aren't as likely to see that same kind of situation.
You really can't go wrong with any of the towers. It all depends on what you are looking for as far as location. Is there something in particular you would like to be close to? Bus Stops? A pool? Lazy River? Zero Entry? Pool Bar?
I've never had a bad wait for an elevator at this resort in any of the towers i've been in. The Worst has been during checkout times on the big checkout days when I may have needed to wait an extra couple minutes for a second elevator because the first one didn't have enough room for my family and stroller because of another family checking out an having all their bags on a cart.
The Presidential units are slightly larger (maybe 50-100sqft tops), and have upgraded furnishings compared to the deluxe units.
I don't rent so I can't speak to how often the big renters will negotiate pricing. As for waiting for the 60day mark for a discount, It's up to you. i don't know if the 60 day discount window is really in play as much anymore as it used to be. the bigger renters, especially as the resort has grown in popularity, will often manage their inventory and set their initial prices with the assumption they will be able to take advantage of the various discounts and tricks available to owners with more points to get the reservation for a lower cost. You could always ask.
From my last trip in october of last year, The "Hard close" of the pools starts around midnight. At that time you will likely be asked to leave the pool area so they can clean and lock them up for the night. (The pools USED to be open 24/7, unfortunately there were several incidents of guests being extremely loud/roudy and pool area vandalism overnight which prompted them to change the policy a few years ago)
Vacation Strategies is one of the major renters which a lot of people on the DIS have dealt with. I would say based off the reports from people around here that the company is reliable and trustworthy.