Maybe all you need is a little inspiration?

https://mashable.com/video/man-excavates-basement-rc-construction-toys

Have you tried to tighten the bolt, then loosen the bolt, over and over again, try to get a little movement to let the penetrating oil work in.

Do you have anything to wedge against the top of the kickstand to prevent it from twisting

Personally, I have never tried to stain concrete, it's just not a look that I like. If I was in your situation, I would level and go with an LVP floor.

Looking at your photos, one would assume the floor is level. However before applying floor leveler, I would verify that with a long level just to make sure

Both are at Home Depot since that is the store closest to me, Lowes will have similar products. The specifications and instructions are pretty straightforward if you want to dive in to the details.

https://www.homedepot.com/p/Rapid-Set-50-lb-CTS-Concrete-Leveler-186010050/204414391

https://www.homedepot.com/p/Sika-SikaLevel-50-lb-Self-Leveling-Underlayment-Concrete-Floor-Leveler-517004/207086698

If it is only 1", I would go with a concrete leveler either SikaLevel 50 lb. Self-Leveling Underlayment Concrete Floor Leveler or Rapid Set 50 lb. CTS Concrete Leveler.

It is the more expensive option but much easier to work with and less risk of cracking.

At 1", 1 bag will cover 5 sf, so you would need 5 bags

You need to prime the floor with an Underlayment Primer

So, $200-$250

The cheaper option would be to use a Sand/Topping mix witha fortifier and the primer, around $100.

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Forms... depending on the working area you can use plywood, 2x4, etc. You just need to make sure nothing can run out of the bottom or corners. The self level has a milkshake consistency if there is a space in any of the forms it will find it.

Does the washer have a drain and spin mode? If so, do you hear the pump at all?

Depending on the washer model, there may be a service menu to allow you to test the drain pump.

Sometimes the manufacturer hides a service manual inside the machine, you have to remove the top and look in the corner next to the drum.

Are the LED recessed lights dimmable?

What is the height for the top stair, versus the rest of the stairs?

https://www.thespruce.com/code-requirements-risers-treads-stair-width-and-more-4120151

Drum sanders are not forgiving, if you rent one, I will guarantee you will have drum marks in your finished floor.

Rent the heaviest orbital sander they have, then when you think you're done, keep going, then when you run out of sand paper, go back to Home Depot and buy some more and keep going. The orbital sander will take a lot of time, but is the best option for DIY.