18-250 almost certainly won't cover the K1's full frame.
Although, saying that, at least the lens will mount onto the camera and you can shoot in crop mode if that's helpful.
You obviously only get 15Mp resultant image but that's still heaps.
(more on this later)

Dunno about Pentax 100 macro tho. Dunno nothing about this lens .. best to check it out yerself.

Sigma 50-500 is a 135 format lens, so no problems with that one either.

As for the crop lens.
After I got my D800E a few years ago, I ummed and ahhed for a long time as to which wide angle lens I wanted to get for it.
Took me more than a year to finally decide(idiot me went to a show and played with Nikon's 16-35/4 VR and the 18-35 AF-S lenses too .. as I had my heart set on a 14-24/2.8.
But I also wanted to be as wide as I could possibly go too .. and thought hard about getting the Sigma 12-24II as well.

But until I actually decided what to do, I kept on using the humble little Sigma 10-20mm lens I've had since I got my first DSLR back in 2006!
While it obviously can't cover the full D800 frame, that never bothered me so much, and always had it in mind to crop the resultant images.
The one significant advantage of shooting with the D800 + 10-20, rather than still using the much easier to frame D300, was that I could crop more than the APS-C frame that the D300 could do.
I could crop the D800 image to a 1:1 frame format, therefore allowing more of the frame to be captured.
So for a very short time, I shot the D800 and 10-20 in Dx crop mode(just to save hassles later), but then soon went back to the full frame and cropped in PP at home once I was happy with the image framing.
Cropping in PP is actually super easy anyhow, as you can batch this in some software easily.
As a rough estimate, I'd say that the D800 + 10-20 lens would give me about a 13mm lens FOV when cropped to 1:1 format, but with heavy vignetting in the corners(which I didn't mind too much anyhow).

After a year, I ended up getting the Sigma 12-24 lens as a temporary wide angle with the idea that I was going to get the Nikon 16-35/4VR lens as the other more versatile wide angle lens(ie. filters and VR and so forth).
Still haven't got the Nikon lens yet!

so, don't be worried about lens use if you're thinking you'd like a new camera to play with.
I'd say at the least getting the K-1 will give you a massive increase in dynamic range compared to what you already have in your camera.
(that was one other significant step up I saw in the D800 from the D300 too!)
Once you have the camera, just use what you have, and can, and are willing to endure .. and then look at new lens options at your leisure .. ie. if and when you can afford/justify them.