So you really think that Comcast doesn't want you on their network with a router spoofing a laptop MAC today?
It's the intent to be somewhere you know (or ought to know) you aren't wanted that matters.
2.
It's not just "I did $5,000 worth of business." If Comcast had a program where they sold "router-attached Internet" for a price difference that totaled $5,000 over the price you paid for "computer-attached Internet" then you would hit CFAA levels.