One circuit or feeder to an outbuilding
If you install a 120/240V split-phase #6 feeder, you have to get rid of the #10 circuit. Then you would feed the well from the subpanel you plan.
The only exception is if a circuit is a different voltage (no luck here), or a different usage - classically, a circuit switched from the source for yard lights, well, etc. If you wanted to do things as you plan, you could always change it so the #10 well line is a switched circuit operated by a pressure switch back at the house.
No elbows -- assemble the conduit then pull the wire
Notice how you couldn't find any PVC conduit elbows and had to steal a plumbing elbow to make that 90? That's because elbows don't exist in conduit. Code requires you assemble the conduit complete empty of wires - and then pull the wires. Can't pull around an elbow. To make turns, either use a sweep, or a conduit body.
Outside disconnect not required
I see you spending some coin to provide an outside disconnect. That's not required.
A disconnect is required for an outbuilding, but it can be indoors. In fact what most people do is choose a "main breaker" subpanel, and use the main breaker as the disconnect. When this is done, the size of the main breaker does not matter. The panel bus+breaker need only be >= the supply breaker.
"But I'm using a main-lug panel that is too small to really have a main breaker!" Um, yeah... about that...
Panel spaces: "Go Big or Go Home" as ThreePhaseEel says.
Nobody ever asked "I need to add a breaker to my panel, but it has lots of extra spaces available. What can I do?" They always ask the other thing.
Painted into a corner because somebody scrimped on a panel, and what was their big savings? At most, a pizza. Spaces are cheap.
For instance in your case, I count 2 wells, a mini-split, and a presumptive need for a 240V circuit for larger tools - that's 4 240V circuits - 8 spaces so far, plus lights and at least 2 more circuits for saw and dust collector. A blink of an eye, and we're up to 11 spaces already - and you picked a 6-space panel which just goes to show how easy it is to short yourself on spaces. So don't make that mistake - select 24-30 spaces and you won't have a worry.
Panels this size also have a distinct, separate main breaker, which creates a better aesthetic than a backfed "main".
Many panels claim "12 spaces 24 circuits" - beware of that claim. The 24 circuits requires use of double-stuff breakers, which precludes use of GFCI or AFCI breakers, which are widely required now. Get 24 actual spaces. They're cheap.
Use a breaker lock instead of well pump disconnects
You don't need a disconnect box for your wells, either.
What you need is a disconnecting means that is either a) in line-of-sight, or b) lockable for lockout-tagout. (NEC 430.102). That way a repairman can be assured that someone thinking about turning on well power will either a) see them, or b) be unable because of a lockout-tagout.
The supply circuit breaker is a perfectly acceptable disconnecting means, and that can be a breaker. So the breaker panel could be in line-of-sight (i.e. outside)... or the breaker could be fitted with a locking kit.
Local grounding rods
You need a ground wire for human-made current. But you also need a ground rod for natural current. Code requires the ground rod pass an expensive test, or use 2 ground rods at least 6' apart.
However, since you are making a foundation pour, and surely including some steel re-rod, seize the opportunity to provide yourself one or more Ufer grounds. Turns out, a concrete slab is an absolutely fantastic "grounding rod", and is automatically approved with no testing. You just need to tie into the re-rod at the time of pour. So make sure your concrete guys do that - they should know the drill.