1. Yes, you can get them in one letter, but ensure that the details are segregated in two sections (duties and responsibilities for each, period, designation, pay, reporting manager, full-time/part time, permanent, location etc)
2. I assume that you are applying under FSW. In your work experience you can mention both the NOCs. For the primary NOC, you can mention the one related to Business Development & Strategy as that is the one that will make you eligible under FSW (minimum one year in an NOC under skill type 0, A or B).