A couple of comments to make the drawing a little clearer:

Sink #1 is the kitchen sink, #2 is the bathroom sink and, of course, the bath sink, commode and tub are in the same room;
they're shown like they are on the sketch just for clarity in how the piping is run.

All horizonal drain and vent runs have the standard 1/4" per foot slope.
The horizonal drain pipes tee into the verticals with a sanitary tee.
The vertical drain pipes tee into the 3" main with combo wye tees.

Increased the main vertical vent from 2" to 3" (It seems to me, however, that the 2" would work just as well, seeing as
how the toilet vent would also be getting venting from the tub and kitchen sink vents; would that not be so ?)

The kitchen sink horizon drain is now 36" instead of 66" and the vent goes 45 degrees for about 2 feet before going vertical within the wall.
(I understand that 45 degrees and steeper for vents is considered vertical)
The horizonal and 45 degree runs will be hidden within the sink cabinet base.
The vent does reduce to 1.5" through the top of the wall to clear a truss that is directly over the wall
(I know, I should have caught that before placing the wall), but since it is venting only the kitchen sink, hopefully 1.5" is sufficient.

Increase the final vent pipe to 4" to come closer to the sq." area of both 3" vents going into it.
(Not sure but if stayed 3", would it still have been sufficient ?)

From the toilet to the main stack, changed from a 90 degree elbow going into a combo tee wye, to a 45 degree elbow going
into a wye. Is that kosher, or should I have left it with a 90 into combo ? (Just seems like the 45 and wye is more of a straight shot)

The main cleanout is not actually under the house;
it will extend about 3 or 4 feet via a 22.5 degree elbow to the edge of the crawl space.

One last thing; I have included cleanouts as shown on the sinks and tub. Should I also add a cleanout just below the toilet
45 degree elbow or is that a short enough and vertical enough run not to need one ?

Thanks very much in advance for your comments,
Arky

As I stated in your previous post, the solution to your problem is much simpler than what you have, however, I need to know what code your under..If you don't know then let me know what city and state your in and I can look it up.

I already have the solution drawn out, just need that code info to finalize it

Some changes are:

By repositioning the kitchen sink slightly, I was able to keep the trap arm within the max 60" length. And was able to keep the vent size 2" by locating it on the other
side of the wall in the pantry room (not ideal, but will not be too noticable behind shelving).

The bath sink, of course, is actually on the other side of the vertical 2", in the bathroom by the toilet.

I decided to go through the roof afterall with the main vent, right next to the ridge.

On the tub, I will put the trap within the floor joists; even though the crawlspace
is open, the insulation between the joists should keep it from freezing (I'm in
Arkansas, so it shouldn't be a problem).

The clean outs are marked C.O. and the one at the end of the main 3" line as well as the double clean out will be outside the perimeter of the crawlspace.

Do you see anything that might give me problems ?

Thanks,
Arky