I would certainly bow to flames and visajourney expertise on the early entry matter.
However, as was mentionned, it is also
perfectly legal for the border officer to deny you entry, particularly since you state that you will be staying in US "until the
K1 gets approved", which is not quite the same as visiting for a specific period and then returning to canada. Not quie the strong ties the officer would be looking for. like: "I will be visiting my fiance for two weeks and then return to my appartment and my job in kamloops".
The "logic" that one must be in the US to maintain the relationship is obviously false. He can visit you in canada, for example. Your relationship is already established: you're engaged! I'm only talking about the period after you submit K1 papers until K1 approval, not years.
More logically, If fiancees were regularly allowed to visit US after being engaged and then subsequently marry, then there would be no need for a
K1 visa program, would there? You would simply enter US as a tourist, marry and adjust status. K1 visas exist for the very reason that such actions are NOT legal.
Back on the work issue, which is not a strong suit in visajourney: Working in US requires a work status. Other than "H" (for professionals) or "L" (which is for intra-company transfers), this would be a non-immigrant status (lets say
TN status for example) that would not allow intent to immigrate, which you clearly have demonstrated by applying for K1 visa. Technically it is the same criteria that would apply to someone simply wanting to visit (which is known as B2 status), however because the requirement to continue to have ties in canada (the "strong ties" that flames suggested) would no longer be there, denial of a TN or similar work status would be automatic.
If the employer
were willing to sponsor you for an H1 visa, and you are eligible, then by all means your employer can apply for H1, hire you, and then you simply move to US and marry, without even the need for K-1. However most employers would not go thru this effort and expense knowing that within weeks you would get your own work authorization and not need sponsorship at all. They would simply wait until your EAD came thru.