But Sir/Mme, you are not looking at a UA issued ticket. You are making a dummy booking on the TK website for a TK issued ticket, which is different from a UA issued ticket. You can't use the info on the TK website to anything when you are inquiring about a UA issued ticket.

To avoid your doubts and any issues, I suggest you book with TK rather than UA. Why do you want to book ORD-ISD-ADD with UA? - when UA is not operating any of the flights. Do yourself a favor and book with the carrier your are flying with. It will also be much easier in case you have schedule changes or cancellations to your flights.

EDIT: I see now that apparently you have actually retrieved your UA reservation on the TK website? Did you enter the TK PNR (is different from the UA PNR) on the TK website and you see that you have 2 pcs checked luggage? If correct, I don't see any reason why you should doubt the info provided to you on the TK website and you are unlikley to face any issues at check-in because the check-in agents will see the same about your checked luggage allowance as you do in the TK website.