Will either or both my computers suffer irreparable damage? Will I loose the data in my PC? Will I not be able to try again?
No, no, and no. What you will have is an incomplete and possibly corrupt user account on the iMac. The incomplete account can be deleted. The possibility of a canceled migration corrupting the iMac's OS is very remote, but OS X can be reinstalled fairly painlessly.
Two days is too long. Cancel the migration, address the effects of the cancellation, find a faster way of connecting the two computers and run Migration Assistant again.