I don't know what the 3 little screws are for. I think you are right though collimation.
If I remember right the meniscus lens up front just has 3 tiny little set screws holding it in the tube, I don't think any adjustments can be made there but a blow to the meniscus could knock it out of alignment very easily.
All these things will show up in a star test.
I went back and looked at your photos and I'm not sure what is holding the meniscus in the black tube. I don't see the set screws on the outside.
The three screws in the back are not for collimation - they are too short. I have one of the orange C-90 Astro models that I replaced those screws with longer nylon bolts and nuts that CAN be used to move the primary. I had my mirror recoated and while it was apart, I figured that weak spring that is supposed to center the primary might not be the best way to accomplish the task. With the new nylon bolts, you can nail the collimation and it stays in place (assuming you have no issues with the secondary). I also flocked the inside of the tube for good measure. I use .965 eyepieces, but I do have a LAR for it. I seem to recall reading there are two slightly different LARs and they don't always fit properly. With the wedge and motor drive, this makes an incredible little portable scope.