No complaints from me....... All looks well. I congratulate anyone attempting off camera flash with Pentax... Its not so easy going....

You cant actually purchase the Sigma 105 new anymore. And they dont make the new verson in a Pentax mount.. So that could narrow your choice.. I had a problem with mine recently. Sent it to Sigma for repair. But they stated they no longer had parts to repair it.. So the Pentax model is looking like a good pick...

2 is my favourite. Though I cant see why you would focus on the brickwork... But street photography is tough... Keep them coming...

Well done on winning the competition... I too should take more interest in these things... Lovely bag well done again....

Cant really answer this as I dont use the software you mention. Only the full photoshop version. But I do use the K5ii. Make sure you are producing your raw files as Adobe DNG files and not the Pentax PEF files and all should work perfectly.

Make sure you download the latest K5ii driver into yout Elements software package... It probably didnt carry it from release...

I'm assuming the triggers are manual triggers and not TTL. So you will not remotely be able to change power settings to the flash. This in mind, any flash gun of any brand will give you what you require. Look for one with manual zoom and manual power settings. Two off camera flash gives great versatility to portraits and the like. For under £30 the world is your oyster on ebay. Keep in mind the older flash guns were very powerful. But tended to have longer recycle times. If buying new the Yongnuo YN-560 ii is a good choice. You dont really need the iii or iv version as they just offer remote power changes. These have become a little more expensive sine becoming very popular. Though you may want to upgrade this option in the future. My personal recommendation if buying new..... The Godox TT600.
https://www.amazon.co.uk/d/Flashes/Wireless-Speedlite-Trigger-Fujifilm-Panasonic...=sr_1_3?ie=UTF8&qid=1487162049&sr=8-3&keywords=godox+flash

Fabulous gesture. I applaud you duster...

The camera is 7 years old....Think its time for an upgrade, to be honest..

If you purchase one please dont do this with it...Even though it seems you can.......

https://www.youtube.com/watch?feature=player_embedded&v=Ni6ZuEvz17w

But the other manufacturers supply triggers or have subsideries that do.....!!