OpenTransport might not run on an '000 processor, at least based on the recollections I have of it, so if everything else works and it looks like you just can't get an IP address, I'd just set a static one in a range that your home network DHCP server isn't using. (I have a Linksys router, BEFSX41, and the default DHCP range therein is 192.168.1.100 to 192.168.1.150, as I recall) so I just statically assign things into little buckets below 100, although I'll probably start going above 150 at some point, just depending on what kinds of devices my network sees in the future.

If it does run on 68000, it looks like OT 1.3 is recommended for 7.5, here's a convenient download: http://main.system7today.com/updates/75x_68k.html (It also has some other 7.5 updates.)