if I remember right from doing it last year the form says you have to explain any gaps of more than three months, so leaving things off doesn't really work. Of course, I couldn't remember all the details of each job--for instance, I couldn't remember the name of a day care centre or my boss that I worked with for four months in college. I just put down something like children's day care centre work and the city, cannot recall address.
If you are stressed about any particular detail, I found them to be very helpful in answering questions. I don't know about the GSCC since I registered with the CCW in Wales to get my GSCC, but they had a helpline and had a person who was specifically responsible for international applicants who was good at answering questions.
I think you are wise to apply from the States. I waited till I got here and found it difficult to go back and gather the information. I didn't have references here to recommend me and didn't want to send my paperwork, birth certificate, passport and such back to my old boss in Idaho to verify. I ended up registering with a social care agency that I didn't really plan on working for just so that they could sign the paperwork for me. It would have been much easier if I had done it there.