Thanks for your input, that's very appreciated -
Indeed, I'm sure the "legal stuff" is all very easy when you have done it at least once ; though for someone who has never been through that process, it's all quite confusing and a little bit scary.
In my case for example I don't have a company, and I don't even know if my "amateur/hobby" "work" qualifies as a "business activity" ; so there are lots of questions like "do I need a company to sell a product, or can I do it in my own individual name", "without a company, what are my personal liabilities", "with a company, what are my obligations", etc. Lots of things that do not really seemed to be explained anywhere. Especially considering it all varies depending on the country (adding internet, international digital distribution, and double tax treaty agreements making the whole thing a big mess for non-experts)
I have an appointment very soon with experts, accountant and solicitors, who will be able to tell me how to proceed
So far I haven't sold anything and I'm not expecting to make much money at all to be honest, but I'd like to do it "right" from the beginning. It's quite easy to just setup an itch.io page and a paypal account, but I don't want to go ahead until I have the confidence it is suitable for my situation (and that I won't have to re-do it after creating an actual company, declaring an activity, etc.) and that I don't expose myself to unreasonable risks.
Also, to make things more complicated, I don't have a "normal job" anymore and I'm just living on my savings, meaning I don't have "normal tax" forms onto which I can claim additional personal income from other activities.
As for the marketing side, I've been trying to do my best ; building a small community of followers during the development (updates, screenshots, demos, polls, etc.) I had "some" success - but without much visibility in the first place, it's quite hard to go beyond the small circles of indie game devs themselves. As for the press and games websites, I've got my material ready (resources, screenshots, trailer, etc.) ; thought it's near impossible to catch the attention of "big" news sites unless an indie game is already a success.
Thanks for the contribution ! Updates very soon...