Hi @samarasArt Iām not a creator, but part of Patreon team in Europe. If youāre filling this form out as an individual, you most likely can leave part 10 blank HOWEVER Iād suggest to have that run by your accountant nevertheless.
It sounds like you have done your research, but here are some links which may be useful for you:
Good luck 
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Hey, did you manage to find your answers?
I am German based, filled the form maybe 3 years ago (I donāt remember lol) and am not sure what I wrote into the form, but if you tell me what is the question asked I probably remember how to deal with it.
Liebe GrüĆe
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Hi, sorry for late reply. I still havenāt figured it out 
This part gives me trouble (highlighted)
- Special rates and conditions (if applicableāsee instructions): The beneficial owner is claiming the provisions of Article and paragraph (???)
of the treaty identified on line 9 above to claim a (???)
% rate of withholding on (specify type of income):
ādigital artworkā
Explain the reasons the beneficial owner meets the terms of the treaty article:
(???)
danke im voraus und liebe grüĆe 
Hi again @samarasArt,
Iām sorry you have troubles to fill in the form, as I mentioned before Patreon is not a registered tax professional, so I canāt provide you with advice on how to fill out this form other than redirect you to IRS instructions for how to fill out the W-8BEN here: https://www.irs.gov/instructions/iw8ben/ch02.html
Here are the instructions for the specifics you mentioned:
Part II
Line 9. If you are claiming treaty benefits as a resident of a foreign country with which the United States has an income tax treaty for payments subject to withholding under chapter 3, identify the country where you claim to be a resident for income tax treaty purposes. For treaty purposes, a person is a resident of a treaty country if the person is a resident of that country under the terms of the treaty. A list of U.S. tax treaties is available at http://www.irs.gov/Individuals/International-Taxpayers/Tax-Treaties.
I hope this helps , good luck 