Yes, under the principal applicant's name.
Even your GCMS note "possible waiver" section telling about the waived scenario. Most probably, second officer (other than the first one who wrote that note) deems the need of interview.
That's why, I think, you got a letter.
Gather strong documents referring to solid proof like phone bills, financial support, your boarding pass, e-ticket etc for the interview.
Personally, I think, sending extra documents won't change anything at this point but who knows, you may try.
I'm so sorry to hear that:at this point, stressing out won't help either. Please don't loose your mental strength and we all pray that your spouse will be with you soon in canada.