How to remove a bent chuck from a Ryobi DP101 bench drill press

take back to HD and exchange it for a new one.

yes, a bent arbor could be causing this... sometimes they can be straightened... or by a new arbor

there is a "drift pin" that came with the tool, you would need to insert it into the slot and tap on it.

When you buy a replacement chuck it will have detailed instructions- at least Jacob's brand chucks do. Basically there is a retaining screw inside the chuck that needs to come out first- it may be left-hand threads . Then you put the short end of a 1/4" or larger allen wrench in the chuck and close it tightly. Set the drill on a bench with the chuck off of the bench and strike the allen wrench with a mallet in a counterclockwise direction. Do this several times, then you'll be able to spin the chuck off by hand. Reverse the process to install the new chuck.

It screws off

First you have to determine if it is the spindle or the chuck assembly. I would go to ereplacementparts.com and look at a breakdown for this tool so you know what the parts look like and then go from there. I couldn't find the schematic on the Ryobi site.

you are half right. The screw that you see is a chuck retaining screw (LH thread) to keep the chuck from loosening up when in reverse. What you need to do is if you have one remove it first and then find a bent handle allen wrench about the size of the chuck capacity, lock the shorter end in the jaws and then position the wrench at about a 30 deg angle and put the chuck on a block of wood or bench and take a hammer and hit it counter clockwise. If you have a wrench small enough to lock onto the spindle use it and brace it on the bench. If this tool has a high and low setting use the low and if clutch equipped the drill only. Let me know if you need more help

remove the chuck retaining screw, shift the tool into the low position and the clutch into the drill only position. Find a bent handle allen wrench about the size of the chuck (bigger the better) insert short end into chuck and tighten. Put the chuck on a work bench with the long end of handle at about a 30 deg angle and hit it with a hammer. It might take a couple times but it will come off. Let me know if you need any more help, and if I have helped you would you please rate my answer accordingly

Make sure bit doesn't have any burrs caused by slipping in a chuck.