No one can tell you how to proceed. This is a decision your son needs to make along with his wife.
1. She needs to get a visa to be allowed to enter Canada temporarily. She cannot enter Canada without a visa. The options are to get a TRV / tourist visa, a work permit (this requires her to get a job offer from an employer in Canada and for that employer to get an approved LMIA), or a study permit (this is an expensive option since she would need to pay international student fees and she will need to make sure her planned studies in Canada make sense in light of her previous education and work experience).
2. See above. If she cannot remain in the US and cannot find a way to get to Canada, then she can return to India and wait out the processing of the spousal sponsorship application there.
3. TRV is a tourist visa. She needs to qualify on her own and will need to prove her stay in Canada is only temporary. Probably a 50% chance of approval.
4. Yes, she can do that. She won't be able to claim any points for her husband's work experience or education or anything else. She will need to qualify and be selected all on her own. Note that there have been no FSW / EE draws so far this year and she will need a score of 470+ to have a chance of being selected once draws start again. Also keep in mind that the processing for these applications is over a year right now.
5. See #1.
