For my undergrad, I mostly focussed on number theory and differential geometry. These topics are mostly useless unless you want to work at the NSA, which only works for the US. Most of my undergraduate curriculum is absolutely useless except for the art of mathematics itself.
For my Masters I wanted to learn more about numerical analysis, hoping to land a job this way. I suppose that did help me understand topics like machine learning, which really seems to me like numerical analysis rebranded, but I didn't end working on anything like it. In fact, what happened is that I started contributing to Octave and used the experience from working on that to justify getting other programming, non-mathematical jobs.
The reason I'm telling this story is just to emphasise that most mathematics is useless, always has been, always will be, just like most art is useless. You mentioned very specific areas and applications of mathematics, but mathematician in general will always have difficult finding jobs pertaining to their mathematical interests and need to diversify towards the need of the job market.
Also, if it really were about that kind of structured thinking, maybe just teaching chess to kids would be just as well.
Anything you can link to to read more about Karl Kempf? A quick google hits linked-in and paywalls.
Do you have more info on this?
Can you hand-code a solver for Maxwells equations or Navier-Stokes (lid-driven cavity flow)? That opens electronics and thermo-fluids. How are you with classic and singular perturbation methods? That gives you signal integrity at Intel - they pay pretty well. Get a few languages under your belt - icky things that are gold plated. MatLab, LabVIEW, Python, SQL, and C. That gives you most of mechanical engineering, lab-based data collection, tons of current "data science", being able to work with previous content, and making your code go really fast, respectively.
Try not looking for jobs on monster, or dice or such. Get friendly with a technical recruiter at Manpower Technical and ask them to get you a few decent contract positions to help you both return some excellent value, and to grow your professional breadth. Make sure some of the positions are business, production, design, and leadership in that order. If you do leadership first without the others, you are wasting yourself.
Read a few books on how to negotiate salary. Your earnings at age 25 determine your total lifetime earnings, so if you let yourself get low-balled early, it can cost you a few million in total lifetime earning. You don't want that.
Once of my heroes is Karl Kempf. Read what he, applied mathematician that he is, has done. He returns a defensible $8 billion per year every year in new value to his company. He is someone to emulate.