I-485: Possible RFE for employment in Cnd while on H1B in US

Hello,
I am a Canadian citizen applying for GC.
On the G-325a form I show part-time work experience with a Canadian client which lasts for almost 2 years when I was already in the US under TN/H1B status working for different employers.
All the work for this Canadian client was done on a rare basis and only when I visited Canada during vacation time. However, this fact may not be very clear from G-325a form which does not allow putting lots of extra details about each employment.
I also showed this experience in my resume and the approved Labor.
Last year I entered the US by land from Canada on a valid H1B, therefore, no stamp was made in my passport since Canadians do not need to be given I-94 or passport stamped when coming by land. I am no even sure whether the entry was recorded in the system, since the guard simply looked at my passport, visa and the picture and handed it back to me. I am not sure whether he swiped the passport or not, it was like 4 am in the morning. If I write an affidavit to include with my I-485 stating that I did enter the US on that date, will the CIS accept it?
I am really worried about the possibility that my GC can be denied or at least RFE issued to prove that I actually did all the work outside of the US, since working self-employed while on H1B is not allowed. However, it is perfectly legal to work in my home country while leaving the US during the vacation time, right?
Any suggestions, ideas?
Thanks!