I don't think that 50-70 dives is a terrible place to start DM training; just don't be in a rush to get to instructor.
DMCs and DMs, because of who they are working with, get a lot of valuable experience. How many panicked divers has the average rescue diver dealt with? Probably none, maybe one. How many will the average DM encounter over 6 months? It depends on the instructor and how training is conducted, but it's not none. This is the level where you'll develop your skills and learn techniques that you'll use when you become an instructor.
The argument when it comes to professional training goes, "____dives isn't enough, you need more experience." But the best way to gain professional experience is to get in there and do it. . .
Are you going to be a great instructor when you take your first class into open water? Nope. Chances are going to be addled, stressed, and make mistakes.
If we were sitting in a bar and you asked me what I thought you should do, I'd say, "First, take a good cavern class." (Good, IMO is a cavern class where you learn in doubles/sidemount from an instructor who doesn't charge per course, but rather per day). Once you've done that, do the SDI DM course. Being a DM is hard work (schlepping tanks etc.) but you spend a lot of individual time with students. Work with as many instructors as you can during your DMC/DM time. They'll all teach you something (including things you don't want to do when you become an instructor).
When you get the bug to move on, take the AI course and spend some time teaching OW with an instructor. Any SDI OWSDI can teach the AI course and then you can teach classes under supervision. Do that until you're comfortable with teaching under supervision, then work with an IT to move on to becoming an instructor. Even if you decide to become a PADI instructor, you'll be miles ahead of the average candidate.
One last bit of advice: military folks are really easy to teach. They can handle a little stress and still execute the skills. As a group, I'd say they are my easiest students. Find some civilians to work with