FG Variance

No.  You’re really getting sugars either way, lower temp is more fermentable, higher temp is less fermentable.  Getting the wort to 170 stops enzymatic activity.  If your batch sparge water is 170 degrees, when you mix it with the grist it will be well below that. 
So if your mash fell a bit during the hour wait, and I don’t think you added any water to warm it up, with the cooler lid off you vorlauf, drain while temp continues to fall even faster now because the lid is off.  I think  Dennybrew.com elaborates a bit on some temps and end of mash additions. 
Essentially what you’re looking to do is raise your mash temp a bit at the end of your mash, being careful not to exceed 170 degrees.

But, as my beer is telling me, it really doesn’t matter much and still tastes great.

I usually calculate for a couple degree higher strike water temperature so that after I dough in and stir for no dough balls and a uniform mash that my temperature doesn’t drop below my anticipated mash temp.  I also have cold treated water on hand to add bit by bit until I get it at the exact temp I desire.

Since I mash in a cooler it is much easier and less time to add cold water to drop my temp a couple degrees then heat up boiling water and add that back to raise temps by a few degrees.  Has worked for me for years with this process.

Getting the wort to 170 for 20 min. or so stops enzymatic activity.  Few homebrewers hold the temp that long.  I know I certainly don’t!  I also don’t worry about exceeding 170.  Maybe I should, but it’s never seemed to be a problem.

Tip:  use ice cubes instead of water.

Not go go down the rabbit hole, but around the 170 figure, are we talking about strike or sparge?

Secondly, are we talking about holding a higher temp. longer?  :o

Neither.  170 is ideally the temp you want to elevate your wort to AFTER the hour long mash is complete.

So you’re talking about a mashout?

Yep, see my original post.

What was the purpose of the gallon you added at the end of the mash prior to sparging? You said you didn’t mash out.

To equalize the amount of wort I would get from the mash and sparge.  I know that the grain will absorb a good portion of the mash water.

I believe there is a bit of efficiency boost this way.  If I had used boiling water, it would have helped with the temp loss too.  For me, the biggest plus for adding the additional water is that it allows me to collect enough wort to cover the boilcoils in my boil kettle, so I can begin heating my first runnings right away.

Just an update here, bottled today and I now show 1.010. The beer is pretty darn clear for me, perhaps yesterday it was tough to see w/ sediment.

Would priming sugar have anything to do w/ a move from 1.008 to 1.010? If not then I feel better as perhaps it’s not as dry as I initially thought.

Gravity doesn’t go back up unless sugar is added. Don’t sweat that 1.008, that’s not at all too low.

Can you confirm which way up and down are on the hydrometer? Which was is “up”?

1.010 is higher than 1.008.

So in my case, it raised up bc of the priming sugar. I think I know the answer to this, but it won’t permanently raise the FG as the yeast will eat the sugar and bring it back down again. Correct?

Yep.