Welcome to the forum, and to the Pentax eco-system. You've done the research and have got some strong plus points for the K1. I don't think there will be any argument over those, so long as you see the full frame format as right for you. There's a whole world of great lenses out there for you to discover, and we are lucky that mostly our individual budgets and financial limitations can be catered to.
Most of us here place a strong value on the ergonomic and usability strengths of the top line Pentax DSLRs, such as direct physical controls and customisation options ..... The K1 is the latest and greatest example of these inherent strengths.
Just to add one personal example of how the "eco system" works for me and my individual budget (ie nearly zero now!) ..... I get my macro type shots by combining a 1970s manual aperture 135mm lens with fully manual extension tubes, using stop down metering, plus a modern radio remote controlled flash system .... And it all works seamlessly with my Pentax DSLR (including shake reduction if needed) ...…
Here's an example taken with exactly that combination of old and new equipment …. and this is with the 9 year old K7 aps-c camera! (so you should be fine with a K1
Here's the camera, flash trigger, tubes and lens altogether.... Pentax truly does bring amazing versatility to us for creative photography on a budget!