The review over at Brickset mentions this exact modification:
Pearl gold windows are fixed inside each gunport, preventing the deployment of cannons. While this seems slightly odd, the lattices can be removed and replaced with cannons, as demonstrated here. I appreciate these options but some furniture must be removed from inside to create enough space ...
There's a nice looking mod on Rebrickable that includes full building instructions.
This includes the following PF components:
2 L-Motors - drive
1 M-Motor - tilt cab
1 M-Motor - boom elevation
1 M-Motor - rotate
1 M-Motor - winch
3 IR Receiver
3 IR Remote Control
1 Battery Box
It's MODification, "My Own Design" is silly.
Also used quite extensively outside of the LEGO community, e.g. in gaming a MOD is altered game code you execute, either to cheat or too change graphics for fun.
So an existing set where you altered things to is a MOD.
A MOC is created from scratch.
The simplest way to get different speeds is by changing the gears. The instructions get you to build it with a 12:20 gear down in the portal axles, so the easiest way to change the speed is to flip those to get 20:12. From memory that will not work because it interferes with other parts of the model.
You can fit two 16 tooth gears in there instead, giving a ...
There is a Bricklink store that sells custom-made train driver rods. I've never bought any so I can't speak to the quality. There are supposedly limitless varieties possible but given that you're looking for one that matches a set you should be able to find some already-made for that set.
Regarding the jamming issue, the most common problem is when the ...
Checking part inventory for this set on Rebrickable I found following part to be unique:
10169 - Minifigure, Utensil Sack / Bag with Handle in Green
Review posted on New Elementary also suggest pilot's torso and legs are new/unique prints.
The rest seem to be released in other sets. Some parts are quite old or have been produced in small number of sets.
I have found someone in this video doing that mod.
The modification consists of removing a part of the hopper wall to let the BWE drop it's output into it from the side.
These are the relevant pictures:
I found building instructions for a BR 23-001-L that has a more realistic look on the pistons.
Here is a pdf tutorial on what to think about when modelling steam engines in LEGO. There are pictures of different examples that has various solutions for pistons.
As both the LXF file and the video are unavailable, I can only guess at the problem you are facing. But if the linear actuator is clicking, it means the built-in clutch is engaging, as the forces keeping the actuator from moving are too large. This can't be solved by adding a clutch gear (even with gearing), as if the newly added clutch gear is rated to slip ...
If there is no need for the bricks to belong to specific sets (as in, it's not important to be able to build some official models from them) then I'd say the best way is to look for ebay bulk brick sales. For around 100$ you can get several pounds or around a thousand semi-random pieces. Try searching for "lego pieces".
You have a lot of resources at hand as a teacher in your community. Have you considered sending home a request for gently used LEGO Bricks in your student's folders at the start of the year?
The parents of your kids may not have any on hand, but will certainly know someone who does!
You may also consider renting them from Pley. Their website allows for set rentals at a discounted rate. I'm sure if you emailed them they might have something special for educational institutes as well. I heard they are running a school program.
I suggest using google to search for them.
When I did that I found two threads on EuroBricks discussing this - here and here. The first thread links to a youtube video that has downloadable instructions. Note that the instructions are 19MB and the website is fairly slow.
You can switch 4 pairs of gears on each end of the crawler (2 pairs in the portal hubs and another 2 pairs inside the gearbox infront of the motor) do this on both ends or you run the risk of broken gears or premature motor wear. I ran 12 tooth gears all the way from the motor to my hubs for a dramatic increase in speed however the torque suffered severely, ...