History is indeed complicated and I agree with much that you say above.
Where I take a different course is that I see the Metis issue and the Indian (as the term was then) issue as two very separate ones.
The Indians were recognized by the crown as the aboriginal landholders and the crown negotiated with them to obtain title in exchange for certain benefits flowing to them from the crown. (I won't get into the argument about whether or not those dealings were honourable for the time and circumstances as I expect that's probably a couple of university courses that I don't have). By 1885 there were both economic pressure, as you indicated, and poor administration of treaties and the Cree attempted to renegotiate their treaty and when that didn't work, some rose up.
The Metis on the other hand were seeking recognition of rights which at the time the crown didn't think that they had as they were not a distinct aboriginal community with aboriginal rights. They occupied lands but with no legal status. The Metis in fact wanted to be part of the new British (later Canadian) colonies and advocated and negotiated for that in 1869. They did win concessions under the Manitoba Act (which were poorly administered) By the time of the NW Rebellion there may have been a backstory but nothing which provided a legal or justifiable right to take up arms against the crown.
Because of the treaties entered into before 1885 the Canadian crown very definitely had been recognized as the "owner" of the lands by the very aboriginals who ceded them to Canada. Citizenship was a much more fluid thing in the west at the time as one had a broad mixture of aboriginals, settlers from eastern Canada, foreign (read European) immigrants and US border jumpers. While the Metis may never technically have been Canadian citizens before 1885 they were, nonetheless, at that time, in occupation of Canadian lands and, therefore, by going into armed conflict with Canada, could be considered in open rebellion.
The term treason (or, more accurately, high treason) is a very technical one and is defined in the Criminal Code to include "everyone ... who, in Canada ... levies war against Canada ..." In 1885 the government charged Riel under the British Treason Act of 1345 (see here:
https://en.wikipedia.org/wiki/Treason_Act_1351 and here:
http://www.languageandlaw.org/TEXTS/STATS/TREASON.HTM) which was a part of Canadian law and which defined "High Treason" to include "if a man do levy war against our lord the King in his realm". The court convicted him on the basis of that act and he lost all appeals. It matters not whether or not the Metis considered themselves subjects of Canada. By virtue of Canada's legal title over the North West Territories by treaty and the fact that the Metis took up arms against the crown "within [the] realm" the act of treason was completed and thereby they were traitors.
:cheers: