So today's evaluation was definitely a step in the right direction! This therapist was new at this place, only started couple weeks ago but is an experienced, retired therapist who does it part time and clearly enjoys her work. 4 questions about his eating habits and watching DS eating banana was enough for the her to see there's definitely something off with his mouth and the way he eats and talks. She said she hasn't seen enough to pinpoint the reason but it's either tactile (not wanting any food / tongue touching the back parts of his mouth) or motor problems, in which case the hands and other coordination problems could be related. It could also explain why he does not want to use utensils and does not want us feeding with utensils because then he's losing control of where exactly he puts the food in his mouth. When he's feeding himself with his hands, he keeps it all upfront (kind of like a squirrel) or when he's eating banana, if I make him to take a bigger bite, he'll use his fingers to push it aside and doesn't use his tongue to move the food around. The tongue thing points more towards motor issues.
When he makes sounds, the simple letters names and phonic sounds he makes there in the right places in his mouth but when he starts saying words and sentences it's all produced again only in the very front part of his mouth. FINALLY someone noticed what I've been seeing all along!
So, independently of what the school therapists will be doing, we'll start seeing this lady as well and work on the feeding and oral issues to see what the problem really is. And we might get DS4.5's OT check out the hand mobility issue to see what she thinks about it.

So, as I said, definitely a step in the right direction!