With everything we’ve all experienced, and what we know now, I wouldn’t recommend sending your passport until they finish processing 5535. Also, you will submit your CV electronically and the ds5535 electronically. The passport is mailed through their courier service and they send the instructions for that via the AIS. If he wanted your passports, he would’ve kept them at the interview. The ds5535 process will likely takes months and when they’re ready to finalize processing, the mailing process takes only days. Don’t send it in.
Also - my experience with one lawyer consult is that unless a firm specializes in ds5535 and specifically with the Montreal consulate , they know nothing about it. This community knows more about it than some lawyers (the one I consulted said that I must’ve said something wrong during my interview, which triggered my ds5535) but we know it’s decided before you even do the interview.