Either one is fine.

We soaked the tank for 2 days in the Evapo-Rust, emptied, rinsed, used a blow dryer, and then added some oil. Checked the tank yesterday and there is some slight flash rusting. Should we soak again or is the amount of rust inconsequential? We plan to add an inline fuel filter as well.
drive.google.com/file/d/1n0n_0kYNjkmr803...AYz/view?usp=sharing
drive.google.com/file/d/1PuKuexG_DqMbIXR...UvR/view?usp=sharing
drive.google.com/file/d/1gnR5BRmI1aS0vV9...mSp/view?usp=sharing

Regarding the spark plugs, I used the advice of MarkT and purchased an Autolite 4054. See pics below of existing and new one. There are slight differences, but is it safe to assume they function the same?
drive.google.com/file/d/1TCKYLiHz-X01CsQ...6Dq/view?usp=sharing
drive.google.com/file/d/19chIJK0baouq7jv...OyJ/view?usp=sharing

 

I think you’re tank is fine just run a little premix until you know you’re autolube is working properly I use the autolite plugs they are great gap to .023 

To confirm, this is the Autolube pump and bleed screw correct?

drive.google.com/file/d/1qFylIrK0eyibEWk...CPn/view?usp=sharing

Yes 

Regarding the spark plug, how tight should it be? I don't have access to a torque wrench. It seems pretty tight, but I'm able to keep nudging it along with a socket wrench. I'm afraid it will be too tight and I'll bust something. I didn't pay much attention when I removed the old one unfortunately.

Careful!  It's not that hard to strip the threads in the head!

Best is to torque...  without a torque wrench the "rule of thumb" is finger tight until NEW gasket touches head and then about 1/2 turn with a wrench.  With a USED gasket, you only need about 1/4 turn after threading in finger tight until gasket is in contact with head. 

You still need to use common sense and feel... "feel" is hard to have when new at this.   I stripped a couple heads by overtightening plug when I was a kid.   I got to learn what a "helicoil" was! 

(I almost never use a torque wrench on spark plugs...  spec is about 10 to 12 ft-lb if I remember correctly.  Manuals in Tech library should have spec... )

 

A couple more points...  after the spark plug has been tightened even once, the gasket is compressed and is now considered "used".  Not a problem at all...  can be reused many times.  Just wanted to clarify that point as the reason a new plug is turned a little more when tightening.

Also, Harbor Freight has 3/8" drive torque wrenches for about $20.  Good investment.  They are a "clicker" type which is very easy to use but can go out of calibration.  I still have my first torque wrench which is an old Craftsman beam type torque wrench with the pointer and scale.  Never goes out of calibration.  I still use it occasionally to check and make sure my "clicker" torque wrench is somewhat accurate.

Was able to garner a 3/8" torque wrench from another neighbor. In looking at the manual, it recommends between 20 and 22 ft-lbs.

Manual pic drive.google.com/file/d/18fLjDpUtG-QvKjI...vcx/view?usp=sharing

MarkT I still have my old craftsman too