Have your real estate attorney help you out. An attorney can walk you thought options you may have to make it easier on all parties.
Yes you can use your ow agent its just going to be tough to find something like this. rent with option to buy are very rare here.
Find an agent to help you out. Its free to use an agent and they can help show you what the true market value of the property is. If the seller is not using an agent they likely do not have a realistic idea of what the property is worth. Its common for for sale by owners to price their properties to high based off what ever they can find online and not take into account other factors like condition.
Down payment is really irrelevant when it comes to resale. Its whatever amount you can afford and what amount you feel the payments are the most affordable for you. The more you can put down the stronger you look as a buyer. The West Loop is the hottest market in Chicago right now so the better you can position yourself for offers the better your chances of getting a place.
Reach out to a lender and see if you qualify. Might not be enough time yet but let a professional answer this for you.
Reach out to your agent and see if they can send you some places.
Ask your realtor to send you a market analysis of the area your looking in.
Zillow is a free site to use. If your property is on the MLS it will automatically show up on here.
If your personal situation will be better off with you selling now thats what I would do. Yes it sucks to take a loss but you will make gains off buying now in a market that will be on its way up for a while. Plus with interest rates stating to climb waiting could really cost you in a few years. A lot more than if you made your move.
A good Realtor familiar with these types of properties will be able to help you out. They will also have access to a more comprehensive list of properties for you.