This is one of very, very few incidences when I would go for a smaller film camera that I can operate quickly, even an AF camera. The Pentax 67 is a beautiful piece of engineering (I never ever use mine without a tripod, and the images speak for that) but it is slow, cumbersome, unwieldly can be difficult to focus in low light and the meter is rudimentary in its decision making, especially in mixed light. If I had a choice, I would take the Olympus OM 4, with motor drive (if you are MF-preferenced), or one of the modern era AF Canons (1N, 3, 5...). Spontaneity and being ready for unexpected moments is what this sort of work is about, and I do not think the 67 is really suited to it. Having said that, you've made a good fist of the image. I am unconcerned about compositional errors in terms of on-the-fly, free-framing documentary and reportage, and the circumstances you have described are indeed challenging.
A DSLR is not the answer. In its blithe automation and speed, it would only entice you to make many, many images and thus draw the whole job out, especially if you shoot bursts and the frames have very little intimacy or differences; professional editors would delete 300 and save just 4 being so ruthless over photographers' laissez-faire with these ubiquitous things. You're lucky then that the editing you do will comprise of maybe a few rolls of film and if technique is good, they'll be very, very sharp pics suitable for reproduction and printing to quite large sizes.