1) Employment letter: My HR gave me an employment letter where there is no mention of weekly hours, but it covers the rest of the details.(I can not ask her to add the hours , since they don't provide employment letters for PR purpose).
If you did not obtain the letter for immigration purposes, what was it for, if you don't mind my asking? My concern is partly the date of the letter, if it is not "recent" or does not cover the full time period of your qualifying experience.
Hours worked per week is a critical piece of information in the letter. If you do not get a new letter, there is a risk. If you want to take that risk, you should attach a written explanation of why that information is missing in the letter, what those hours are, and that you are attaching photocopies of your paystubs as proof. Then do that. No need for a lawyer or affidavit.
Yes, the the fact that your paystubs are bi-weekly is a problem. But unless you have other proof of weekly hours (e.g. time sheets) I'm not sure what else you can do.
2) I am here on my work permit , which is getting expired in the first of Aug. My employer is working on getting my permit extended.
Note that if your employer is applying for an LMO, s/he will have to indicate hours worked per week as part of the application and job offer letter. See if you can get copies of that.
Per my understanding, I don't need worry about my communication/residential address since I have provided my email as my main communication mode. What do you suggest?
WRONG. Just because CIC has your email address does not mean they will always choose to use it. You need to update your mailing address as well, or if your new mailin address is the same as your residential address, say so.
b) I am planning to opt CPP-O as VO in my application. Per my understanding, I don't change the VO even if I move back to India ( since I am submitting my application before I move back to India). Is my understanding correct?
You don't have to change your VO; you can request it, but CIC does not have to agree. Your main concern would be (1) slow mail between Ottawa and India, (2) if you are approved, getting your passport to Ottawa, and (3) unlikely but possible - you get called for an interview. It is not clear what the reorganization means for interviews, whether it would take place in Ottawa or be transferred to one of the remaining US consulates.