Kudos to you !
Your 1/2” of smoothing it in a couple spots is more than likely ok
Most manufacturers stipulate it should be within an inch.
obviously you want it as level as possible and you definitely want all the paver tops and all around the bottom rail the exact same level.
In the middle the sand may or may not be helpful with smoothing lol.
Keep in mind that people dish out the middle so a spot or two won’t hurt anything it just may be a little lumpy.
With sand you will end up with some divots at some point anyway.
You can rent a transit/laser level from a big box store if you need to.
We used one to confirm our top rail was maintaining its level as we filled & it was comforting to see.
as far as the gravel dust. It is commonly used although I have no experience there.
@phonedave may shed some light as to how important it may be in your area/with your soil.
A couple notes as you go along on this journey…
While doing everything alone is admirable, putting up a pool wall and a liner alone is not generally recommended for newbies.
This is mainly due to the time it takes to go at it alone. Its kind of a race against the wind and weather so more people/hands is better. The sooner you can start filling the lower your risk of wind damage is. If you must take a break whilst building be sure to secure your walls to help prevent damage (bungees staked into the ground is a common method)
I am sure you have probably watched a million videos but you will probably see this in some of them - along with using rubber tipped clips to temporarily secure the liner as needed.
Never fill at night- just resume filling the following morning once the sun wakes up

Ideally you would start on the wall early in the morning and be filling the pool by the afternoon when the sun is shining and helping with pliability.
Throw a pool raising party to get help
You likely already have this bookmarked but I’ll leave it here for you anyway
www.troublefreepool.com