I am not familiar with MacTCP, but glad to hear you got connected. What do you mean by "couldn't do anything"? I think you should try Navigator 4.05, (The last for 68k 7.5) which will have immensely better standards support than 2. If you want to run 7.6.1, you can go to 4.08.

16MB of RAM is recommended for all of these, how much do you have?

http://sillydog.org/narchive/full4.php