Welcome, and

The 18-250 and 18-270 are also available in their native 'Tamron' versions.

Since you want a 'walk about' lens, it's worth checking the weight of the lenses before you buy, as I personally find the weight of a lens increases exponentially in relation to how long I'm carrying it, especially when mounted on my K20D which itself is no light-weight. I found one answer was to upgrade the strap from the Pentax one.

The K20D does have AF Fine adjustment - C Custom Setting: 35. AF Adjustment. Page 106 of the manual.

I was referring to the Viltrox JY-670 mentioned by the OP

I've had two of the Centron types and the only issue I've got with them is that the batteries go in the body of the flash unit and the whole unit is connected to the end of the lens.

Should work ok. Why do you think it won't?

From Amazon specs;

•Compatible cameras: Canon, Nikon, Pentax, Olympus, Samsung. With host adapter: Sony

From Viltrox site;

Compatible camera Camera with standard hot shoe

How many shots taken with the camera please?

Also, 'less than a year old'; bought from a Pentax Pro dealer, i.e. 2 year warranty?

Welcome!

Fingers crossed. Litigation could be expensive!

No personal experience, but I wouldn't go straight in with a lawyer - they're expensive and there's no way back!

Why not contact them yourself, explain why it's your image and how you prove it*, point out the error of their ways, set out the consequences of their actions unless they cease and desist (or settle), name a price, then see what happens? Give them 14 days.

If they don't settle the matter, unleash the lawyer!

*It's a cityscape at night, which anyone could have shot. What is unique about it that proves beyond reasonable doubt that it's your image, and why/how do you own the copyright?

What have you managed to fit in it?