Some of you guys love reaction rods, while I don't instead.

Hence reaction rod is no different that just  vise clamping the barrel, and the real torque to the upper is at the upper receiver instead.
Worse yet, if the barrel extension was not installed at 150ftlbs of torque to start with, you do chance spinning the barrel nut off the barrel with a stubborn barrel nut being removed as well.

So myself, will always use a clamp shell upper vice block with insert to back up the upper receiver, since it going to be the area that is going to see the majority of the torque when both installing and removing the barrel nut. If the barrel extension pin is loose the socket slot, then soda can to make some small sliver shims solves that problem as well to hold the barrel indexed correctly.

As for the receiver extension pin, and even the dent in the upper barrel socket, no the end of the world.

The extension pin can be drilled out and a new one punched in.  Just don't over drill in depth,  and try to use a mill to cleanly center drill the pin out with a slightly smaller center drill.  Hence slightly smaller center drill and as you are getting close to the bottom of the pin, the receiver extension pin  will spin out with the drill bit 99% of the time.
Note, if you don't have a mill, then take/send the barrel to someone that has a mill.  The last thing you want to do is enlarge the pin channel, or over drill the pin to deep isntead.
http://www.jsesurplus.com/ar15barrelextensionpinpinonly.aspx

As for the dent in the upper receiver barrel socket slot, cut piece of a soda can to shim the barrel in index before the barrel nut is installed, and Bob is your uncle.

If you don't have a mill, check in your home town forum for someone close that does, and it it will only take a min to remove the remnants of the old pin.   The extension pin is just .125" by .250", and easy enough to make a new one of of some A1 or O1 drill stock to punch back in, or just off the end of a 1/8" drill bit if you really want to be lazy instead.

Hell, if you where local Denver area, would have you stop by to just mill the what left of the pin out with a center drill, then make new receiver extension pin to reinstall as well (have plenty of 1/8" drill stock in the shop).

Have never had problems with a upper vise blocks, since it supports the upper receiver right behind the upper barrel socket, and has an insert to prevent the vise block from denting in sides of the upper channel when the upper with block is vised down to cause carrier bind afterwards as well.


https://www.brownells.com/userdocs/skus/l_080000659_2.jpg

With the twin pin type blocks, have seen take down lugs bent, or cracked off when you run into a stubborn barrel nut isntead.


With reactor rod that use the ejector port as the secure point, ditto on damage to either the ejector port, or sheared extension pin on stubborn barrel nuts as well.

Hell, most of the time, you can spin a barrel nut off by just sitting on the receiver, but when you run into a stubborn barrel nut, here is where the upper claim shell  vise blocks shine.