This is still all very vague. I'd like to avoid putting words into your mouth, so tell me if I'm being clear here: you think Russia will be able to domestically manufacture all the necessary high teach weaponry to achieve a stalemate with a country currently being supplied with Western arms, by themselves? If that's not what you mean and I've misunderstood, I'd appreciate clarification, and if it is what you mean then how?
Re Russia having their own industry: you're conflating the existence of industry with the ability to obtain or create the necessary technology to get at very difficult to access raw materials. Russia is currently reliant on the West for this expertise and tech, we know that. Are you saying this is going to change, and if so, how will that happen?
In terms of the economy, around 60% of the global economy currently belongs to the countries sanctioning Russia, and a good chunk of the rest is the Chinese who are observant of sanctions. Nobody thinks some of the rest of the planet, who aren't a monolithic bloc, won't trade with them at all, particularly not the sort of trade that doesn't involve going against the US and Europe on sanctions. The question is how Russia are going to be able to weather the economic damage we know has happened and is still happening, whilst also being able to continue this very damaging war. You argue that sanctions will eventually be seen as damaging to the West, but that completely ignores the fact that energy and economic security are both part of that picture and both threatened by reliance on Russia. It's also simply a prediction, so again doesn't tell us why you're using the term 'fact'.
As for putting words into mouths, who said anything about Russia being on the brink of collapse? That's a strawman. There's a vast gulf between ceasing to function and being able to sustain a lengthy and costly stalemate war. You claimed the latter to be a fact, and you've still not evidenced this.