I think you are not the only one with this issue. There are many folks out there facing a similar issue. As per my past experience, it is mandatory to have the company issued letter with the roles and responsibilities listed out (matching to the NOC that you are applying), Start and end dates (if applicable) and hours/ week listed out. All other things can be optional. I know there are lot of folks out there who are getting reference letters from their managers/seniors but I am not very sure how much weight-age this has with the Immigration officer. This might again depend on the officer that you are assigned to. I personally do not have good opinion on this based on my past experience with CIC.
With respect to the calls, it is always a risk. But we'll have to deal with it and hope that they do not call our employers. I am sure they do not call for 100% of the cases, so let's hope for the best.