My "source" is 13 years in Japan living with Japanese wife, children & extended family :-)

But I'm not going to argue - for example, it may just be that here in Kansai we use them differently. We would definitely say "sumasen" for the things you listed. Just shows how hard it is to get this down from textbooks.

Hmm it is true that I have only hung out with mostly people from kantou. Thanks for the new knowledge, will go look into it. :D

[Edit] Just checked with the friends. It seems like it really depends on the social habits. If a bunch of people started with gomen, then that word will stick, even if it feels weird.

For me, because I started with "arigatou" with them, so my friends naturally used "arigatou" around me instead. However, whether they use "arigatou" or "sumimasen" really depends on their family habits. Currently it's split 30(arigatou)-70(sumimasen) amongst them. Much nuance is learnt today.

I'm surprised you didn't mention the less formal Kansai local term: "oh-KIni" おおきに: It is also used as "Thank you" in casual situations, but my understanding is that it is literally "Excuse me".

So much of proper speech is dependent on who you are with and their preferred idom. Of course formality in the case of uncertainty is usually preferred, but that can lead to both humor and embarrassment.

大きに (おおきに) is interestingly an abbreviated form of... 大きにありがとう (ookini arigatou), in which 大きに just means the same as とても (totemo), so "very". The equivalent in english would be to say "very much" instead of "Thank you very much".