@Quincy Mingo I'm a local lender in Chicago and can help you navigate this. There are a few missing pieces to your situation, and I can answer your questions too.
When was the property deeded to the LLC?
Are you and your partner both 50/50 on the existing LLC?
FYI, you should not be using a LLC on a residential property when you only have one. It's pointless and only causes issues. Whoever coached you into that when you bought it steered you wrong, and now 4 years later you are seeing how it's problematic when it comes to an exit or refinance.
Without the LLC, if you were on title jointly, even with the loan just in your partner's name, you could have just done a cash out refinance into your name, without the hassle of a purchase transaction and down payment.
As it stands now, assuming you are 50/50 owner of the LLC and not a majority owner, the only way to do this is a purchase transaction to buy the property from the LLC. You will need enough funds for both the down payment and also the buyout of your partner.
The only other option that I can think of is to deed the property back to you individually, and then you will need to wait 6 months, and then you can do a cash out refi into just your name. If your partner can wait for that.
As for the purchase questions, you do not need to use a realtor, and yes it is customary to use an attorney in Chicago. You probably only need 1 attorney, because of your relationship with your partner, who will represent the "seller" for title and fiduciary purposes, and as the buyer you really don't need your own unless you feel like you need to protect your interests.
You absolutely should not transfer this property back to a LLC once you own it, especially in the first year as a primary residence, but also because it's completely unnecessary. Instead, go get an umbrella policy on your homeowners insurance for protection, and you can deduct the exact same expenses on your personal tax return as you can with a LLC. LLC's are really only needed for commercial property, and/or once you hit your 10 property cap with Conventional financing where you can't use that anymore.
Lastly, as for capital gains, the only way to avoid them is living in the property for 2 out of the last 5 years. Or deferring them with a 1031 exchange when you sell. Otherwise you're paying taxes on the gains. I'm not a CPA and maybe there is some other magic solution, but in 25 years doing this, I don't know of any.
Hope that helps. Feel free to reach out if you want to deep dive further.