Wide-angle weather-reistant lenses for Pentax?

The Sigma 10-20 arrived today. I bought the f/4-5.6 instead of the f/3.5 version, because the f/4-5.6 was significantly less expensive and if I like the lens but eventually want f/3.5 then I'll sell the f/4-5.6 and buy the f/3.5.

The f/4-5.6 is better than I anticipated. It's not going to be my favorite lens though, so I'm considering returning it. Overall, the quality is OK but not great. On the other hand, it seems to be the least expensive of the options that I'm considering.

It suffers from three problems: color fringing when the sky is the background and objects are in the foreground (the 3rd photo in this post is an example that's a bit harsher than what I saw in my test: https://www.dpreview.com/forums/post/59206494), softness toward the edge of the frame, and significant perspective distortion of nearby objects when photographed at wide angles. The color fringing and perspective distortion are probably fixable in post-production with the right tools and patience, and the color fringing doesn't seem to affect indoor photos.

For someone who's shooting indoor photos this lens would be a cost-effective wide-angle lens. However, as I plan to shoot outdoors, I'm not sure that this is the lens for me. The merchant has a generous return policy, so this lens may be heading back after I have the chance to compare it to the Pentax 12-24 and/or the Sigma 8-16, both of which are more expensive but also seem to have more favorable reviews.