In short, it seems you're trying to use a tool for doing something the tool is not fit for doing. Game Lab was designed to create games, so it's wayyyy easier to draw stuff, do animations, control things with mouse and keyboard, detect collisions, etc. App Lab was designed with different needs in mind (I can't speak for the creators, but my guess is needs that more closely match the code.org's CSP curriculum )
That means you'd have to manually and tediously program your own collision detection as looks like what your code is doing (or trying to do - I'm not sure since I just glanced at it and just a grid appeared on screen when I hit Run).
If this is for the AP exam, personally I'd tell my kids to stick to something App Lab is better at dealing with. For more ambitious kids with more time on their hands, I'd tell them to do Unit 3 in the CSD curriculum and that's probably enough to make a maze game in Game Lab. However, I haven't thoroughly thought about whether there's enough in there to satisfy all the Create task criteria. (Also, it looks like there's stuff in Game Lab that isn't taught in the CSD curriculum, such as for-loops, but I guess your students can combine the concepts they learn from both curriculums.)
I would generally stay away from switching platforms, especially since you say your students are uncomfortable with the idea, but I think it's doable for your students who are feeling intrepid (but heads-up that they're sorta on their own).