Grad school (R1 institution) -only positions at primarily undergraduate institutions (PUI). My undergraduate university's math department was about 50-50 long-term lecturers: adjuncts, but even now they've been moving more towards adjuncts because they get to pay them significantly less than full-time lecturers.
Grad school (R1 institution) had 2 full-time (non-tenure track) lecturers which were really hard for them to get that position. All the other teaching positions are either done by research professors or adjuncts.
Your PI is correct in that pay is not great. From what I've seen on the high-end you're looking at about $70k if you get that full-time position (possibly higher in places like CA or NY). I've seen some adjunct lecturers making less than $20k a year while teaching 3 semesters a year, including summers, and spending 40-60 hours a week teaching.
I do know one science lecturer that what she is doing is she teaches at a private high school in the morning (teaching science classes) then she teaches at a community college in the afternoons Tues, and Thurs, and at the R1 institution (science lab classes) MWF. She also figured out how to juggle teaching some online classes in the middle of all of that. She works 40-50 hours a week and makes 80-90k combined. She said getting the right jobs that would work together was tough, but she knew what she wanted and sought out the exact positions that would make it possible.
Mathematicians are popular in certain parts of the tech industry so if you haven't already you might consider learning some coding by yourself. If you have the self-learning/self-taught skillset most PhDs get then you should be able to learn enough coding to get a job that utilizes your math knowledge. If money is an issue, you could get a job in tech to supplement your income while you teach, especially since most lecturers don't need a lot of outside prep time for their classes so based on hours you'll probably be teaching part-time even if you're hired full-time (once you get 1-2 years under your belt and already have lesson plans created).