Let me try
2) You'll be receiving Med Req in the next few weeks (I mean your wife) and they will send you forms for each family member (your wife, your kids and you).
1) Your situation has happened recently with several member in which primary applicant and spouse are not in the same country. Your wife and your kids have to get the exam in US, and you have to get your form (somehow) and get the Med Exam in Singapore (find DMP accepted in the area). Then you'll have that DMP send Med Result DIRECTLY to the Ottawa (not the local VISA office - DMP might be confused with the situation).
Or the easier solution for you is that to take 2-3 days off and flight back here to US reunite with your family and get the Med Exam together
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My 2 cents,