Good to have a CO detector on every level of your house, especially given the absence of any sort of exit flue for your stove. In my stove, the fireplace damper was removed to allow more width for the 6 foot stovepipe to fit thru the opening and extend up into the chimney, but you might be able to squeeze the pipe narrow enough to get it through the fireplace damper. Others might have an opinion, but I'm not sure I'd wait for warmer weather to get that pipe in there. Let the fire go out and the stove cool down, and clean out ashes before you attempt anything else.
If your son can shake the grates, he can probably help you slide the stove out far enough to get the stove pipe behind the stove and pushed up into the chimney. Hold the pipe up with a broomstick while sliding the stove back in. If there's enough clearance between the top of the stove and the top edge of the fireplace, you can use a hammer to tap the collar/lip of the stovepipe to make a good fit into the stove. If not enough clearance for that, from inside the stove, use a vise grip or pliers to pull the edge of the stovepipe into the opening and seat it well. If you have to use the vise-grip method, to get to the exit hole, you have to remove the baffle plate near the top inside of the stove. It's fairly heavy, but pull the front edge of the plate towards the front of the stove until you can rotate that front edge downward, and you'll see how you can rest the plate on the U-shaped firebrick retainer while you're getting the stovepipe well-seated. Then, rotate the BACK edge of the baffle plate up to the "shelves" that hold the baffle plate, then lift FRONT edge of plate all the way and allow the plate to slide back into position. It is possible to take the baffle plate out of the stove, but for me getting it back into the stove has always been a real pain unless I remove the firebricks, for some reason