Jonathan

I don't know if starting and running at full throttle is harmful, but I usually start at half throttle and let the engine warm up for a couple minutes. Then use full throttle while blowing the snow.

I spray the chute, augers, impellers and impeller housing with WD-40 at the end of the season to help prevent rusting from moisture during the summer.  I have a corner in the garage where I can store it, covered with an old sheet.

Is it possible that the choke knob is not positioned properly on the shaft it fits on to? It should come off (pulling by hand or prying with a screwdriver). You could then try to move the shaft all the way to the left by hand or with a screw driver if it has a slot. If that fully opens the choke, then push the knob back on so that it points to the open position.

The fork is shown in Ariens Parts Radar in the Ariens web page. Plug in your model number and find the fork under "Friction Drive".  I can't decipher how it is held in, but someone else may be able to.

If you haven't done so already, I would suggest you check the Attachment/Clutch Brake adjustment and Traction Drive Clutch adjustment as outlined in your manual. This could be your problem if these belt tensions have never been adjusted. It also wouldn't hurt to check to make sure that your shear bolts are intact.