#(except Tumblr apparently they don't have a Catalan version so I get Spanish. My Spanish is. Abysmal)

[loubatas]

If I may add a bit of my experience, as an Occitan (passive) speaker

I was taught Occitan Provençau at school, because that was my local Occitan dialect. With Vivaroaupenc and Nicard, it's probably the farthest Occitan dialect from Catalan, and I can't understand spoken Catalan, except maybe Rossellonès which is spoken in Catalunya Nord. The accent is too different for me to be able to recognise the words, and the same would happen to a Catalan speaker if they heard Provençau or Aupenc However, I can read Catalan without too much difficulties. The spelling is a bit different between the two languages, but Occitan already has two spelling systems so learning Catalan's wasn't much of an issue. My reading comprehension is a bit limited ofc (I wouldn't read a whole book without a good dictionary) but enough for news articles or webpages

Lengadocian is one of the Occitan dialect the closest to Catalan, especially between Lengadocian meridional dialects like Carcassés, Narbonés or Tolosan, and Rossellonès/Català septentrional. There are quite a lot of Lengadocian speakers from there who have no issue understanding their Catalan neighbours, and vice-versa And as you also mentioned, Gascon (especially Aranés) is also very easy to understand for Catalan speakers

Basically, it works as a linguistic continuum: if you speak Occitan, the farthest away you are from Catalunya the hardest it will be for Catalan speakers to understand you, and vice-versa if you speak Catalan with Occitan speakers. Written mutual comprehension is a lot less variable between dialects because you remove the accent component, so it's mostly a spelling and vocabulary issue and a few minor grammar differences (which can also exist between dialects anyway)

That being said, it's quite easy to get used to each other's accent through exposure, and once it's done that removes the biggest comprehension barrier. The main reason I don't understand spoken Catalan is because in France, outside of Catalunya Nord, you have barely any exposure to the language (I already have to go out of my way to keep/regain my Occitan proficiency, thank to the fucking French state's language policies)

Is Occitania part of the Catalan Countries?

No, but we're similar. Catalan and Occitan were for many centuries considered the same language :)