Welcome to PF John. You do get lots of helpful advice here, as you can see.
No bad choices with any of the camera options discussed. I've got the K-3, KP and K-S2 (which is similar to the K-70). They are different, but all good cameras. Many of the pros of each have been mentioned already. I'd just add these comments:
K-3: robust construction, faster frame rate, bigger buffer, bigger battery than the one used in the KP/K-70/K-S2. It has better AF and better exposure metering than the K-S2/K-70. If you are buying used, this is a safer buy, because it is designed for a longer life and isn't prone to aperture block failure. If you get one with a warranty, so much the better. The dual card slots and top LCD might not be big selling points for your uses. It lacks some of the features of the newer models (e.g. articulating screen, pixel shift, high ISO capability), but it's still a very good camera. Ergonomics are outstanding IMO.
KP: compact size (although only slightly lighter weight than the K-3), but still quite robust construction. AF and AE match or exceed that of the K-3. Small buffer makes it less good for sport/wildlife - although it doesn't sound like that will matter much to you. In the EU it comes with 3 hand grips. People have different feelings about the ergonomics; personally I find even the large grip a bit small and prefer the feel of the K-3. Pixel shift is a great feature for landscape/still life. Three control wheels are good. Tilting screen is an advantage over the K-3 when shooting in LiveView, whether low to the ground or high up. Built in wifi. Lots of other features too, like advanced bracketing. If your budget will run to it, I think this is the model to get for your intended uses. It's been heavily discounted lately, making it a very attractive option.
K-S2: Nice little camera. Compact and light weight. Relatively simple layout makes it easy for someone new to DSLRs. Fully articulating screen is great for macro and selfies! (More versatile than the tilt screen of the KP, although possibly not as robust.) Built in wifi. The 20mp sensor is very good - not far behind the K-3's, but the exposure metering is well behind the K-3 and KP. There have been reports of aperture block failure with this model, and it doesn't have pixel shift, but it still quite well featured compared to other entry-level cameras. Don't expect the same robustness or durability as on the K-3 or KP.
K-70: Has all the good points of the K-S2, with the addition of 24mp sensor, pixel shift and better high-ISO performance (amongst other things). Still lacks the exposure metering and AF system of the KP and K-3, and their robust construction, but a feature packed camera for a modest price.
If you get the KP, K-70 or K-S2, be sure to get one or two spare batteries.
As for the lenses, I think the DA 18-135 and DA 55-300 PLM combination is a great kit. The DA 16-85 might be even better (the extra 2mm on the wide end are very useful if you are not also getting an ultrawide lens, the HD coatings are a big plus and it has better corner/edge sharpness), but it's significantly more expensive than the 18-135. Similar weight but bulkier. Plenty of samples with these lenses here:
DA 18-135 WR, Show us what it can do - PentaxForums.com DA 16-85 WR,show us what it can do. - PentaxForums.com
With a versatile two-zoom kit like this you can add specialty lenses later (e.g. a wide-angle lens, macro or low light/portrait lens).
Leave some money in the budget for a flash too.