Yeah, if the smoke was weaker than you'd like, the initial open grate cooking can be longer, as well as a heavier smoke output from the source. When you described them going from fall apart to basically a stiffer and somewhat drier steak, that was my first thought...go a bit longer on open grate, less foiled and less on the final stage. You should be just setting up the sauce a bit. After the foiling, it probably won't take very long to dry them out, so a 15-20 minute open grate ride would do the job. Due to marinating, you lost some firmness in the meat, so that may have had a big impact on that initial fall apart tenderness when you foiled. I do think if more smoke is desired, 3-0.5-0.25 would get you a lot closer to very tender with a slight firmness to the surface and a light setting of the sauce. Now, that's if you were to use the same marinade recipe and time. With shoulder cuts, they're more forgiving than chops, as they have more collagen and fat, so they can take a higher finished temp. If they got dried out and began to toughen up at the end, it was just too much for too long.
Oh, I didn't think about this until right now, but a longer marinating may cause a reduced smoke reaction as well...being the acidity begins to break down the meat fibers on the surface, the smoke may not want to stick to it as easily...not sure on that, just a theory. I do remember reading about courser dry rub particles attracting more smoke as well. That said, maybe, just maybe, a salt brine would be the best route to go...brine will also bulk-up the meat with water while a lower salt marinade won't as much for retained water, so brine may help during the last hour or so of cooking, to have enough left inside so it doesn't get as dried-out. After all, with shoulder cuts, a truly tender piece is basically getting the daylights cooked out of it, so to have that extra edge may be all it takes to keep it moist.
I did some digging through some old threads I started on small cuts of brined pork...this may give some more insight on what brining your pork steaks & chops can do for you. The chops and CSRs I did were straight smoked, no-foil, but I did get a smoke ring and a good amount of smoke flavor on all of these. I tried to right click on the pics to open in a new tab to zoom-in tight, but the image is from somewhere else...dunno what's up with that...but you can see them pretty well, anyway. Also, for a closer view, push ctrl and +, and keep tapping + until it's at the zoom you want. To return to normal view, push ctrl and -.
I don't know if there are very many others who have posted on this or not, but in the advanced search you may find more.
Hope this makes sense...I'm just trying to piece together the puzzle here. I haven't brined any small pork cuts for quite a while...liked doing it and enjoyed the results, but my interests have turned towards other methods since then, so I'm relying on memory and old posts to figure this out.
Let me know if you need to pick my brains more...LOL!!!