I think you nailed the Multicam pattern, both in terms of the colors that you used and the size of the pattern for the scale. Those figures look great too, who makes them?
The only thing I would do would be to make them a lot dustier, just some sand colored pigments should be fine. The dust and sun wear out the uniforms pretty quick and the pattern will turn almost monotone in places like the knees, seat, elbows, the gear especially will be very dusty, almost looking shades lighter all around just because at least the pants and tops are washed, whereas the plate carrier and pouches are usually not. One thing to note though, sometimes when guys wear the combat T shirts out on patrol, they will look a lot brighter/newer than the pants, just because they wear the pants all the time, but have to wear their thicker zip up tops day to day if they're on a large FOB. So the combat shirts might get worn a far fewer times a week depending on the tempo of operations. I wouldn't worry about the combat T shirt differences in 1/35 scale- but I do still think the guys should look a lot dustier. Even if you just did a light overspray with some sand colors out of an airbrush to tie them all together I think you'd be fine.
I will say I think the slings are fine the way you have them. While plenty of people do use the 3 point sling, most Infantryman and soldiers that have to operate their rifles complain a lot about 3 point designs. They rarely work as they are intended to and often hamper operation of the bolt release and can get tangled on gear much easier. Usually, you will see a lot of one point slings or what are often referred to as 'wolf-tails' -simply a few inches of nylon webbing and a plastic clip that attach to the weapon at the but stock or near the charging handle around the buffer tube and then loop through a D-ring or MOLLY webbing on the shoulder of the plate carrier.
Designed strictly as a retention system though, doesn't take any of the weight off of the soldier's arms like a sling would so they have to basically hand carry the weapon, but way more maneuverable and hardly gets caught up on anything. That's why its usually used for mounted operations or CQB environments where the soldier is basically dismounting, clearing a compound, then mounting back up. For a foot patrol you'd probably have the 2 point sling as you've done. Even a full sized sling set up in a one point mount doesn't wind up working well over a long period of time because they're generally worn too loose to really take up a lot of the weight of the weapon system, they tend to just let the weapon dangle and bounce off of knees when the soldier isn't holding on to it. But again, works great for a short amount of time.
www.brigadeqm.com/.../bmd05.htm here's an example of the wolf tail/wolf hook one point.
And an older version of a two point/one point adjustable sling from Magpul www.midwayusa.com/.../magpul-ms2-multi-mission-single-point-2-point-sling-nylon <- if you click on the tan/FDE color option you can see the back plate mounting option some guys use for their one and two point slings.