SPI Read returns only 0 in slave when I hook up SS to INT
You should check the settings of the TRISB register. Read section 4.2 of this document (http://ww1.microchip.com/downloads/en/DeviceDoc/39582C.pdf). It explains how the TRIS (tristate) registers control the input/output behavior of the PIC16F family. If TRISB[0] is set to 0 then the RB0/INT pin will be outputting low and overriding the interrupt mechanism.

I've lost many hours to that little register in the past.