Can I ask why your visa extension is not happening even after you have an I-140? If you wish feel free to ignore this question or reply using the a private message.
You have a couple options. the first would be to file for Canada PR (Express Entry) from the US and take a long holiday outside the US while you wait for the invite. The other is to move to Canada on a work visa and file PR when you get there. Having a job in Canada when filing under Express Entry almost guarantees you a PR.
Another recent change thats in your favour is that the government has reduced work visa processing time down to less than 2 weeks. Either ways you will have to begin your hunt for a job in Canada soon. I’m working on a blog post to help people with this hoping to publish it later today.