Hi Christopher,
OK, you're making progress, don't give up!

You have ADCON1 = 0 which will have all 13 analog pins set as analog, you probably want to turn the analog stuff OFF by setting ADCON1 = 15. For example RB0 and RB1 are AN12 and AN10 respectively but they are also the SDI and SCK pins for the MSSP module - that may or may not be part of the problem.

You have CMOCON = 0 which will leave both analog comparators ON, to turn them OFF on the 4550 you need to do CMCON = 7 - may or may not be part of the problem depending on exactly which pins they are on and what you're using, or trying to use, them for - I haven't looked into it.

The MCP2515 SPI timing diagrams show the SPI clock idling LOW. You have SSPCON1.4 set to 1 which will make the clock idle HIGH, ie wrong polarity.

Well, that's three things I see that may have something to do with it. Try adressing those, then try capturing the signals with your scope and see if they look anything like the timing diagrams in the MCP2515 datasheet.

/Henrik.