Hi,
1. I thought that your 404 problem was with paypal ? not with jomsocial ? I'm not following you...
2. That's a new problem. It was working before so I assume that you changed something like deleting the associated module which is used to display the products below the categories listing menu. You should go to the menu Display->Content menu, edit the menu 28 that you created and make sure that there is still an associated module. Otherwise, you could recreate the menu and it would recreate the associated module.
3. As I said, you should use another editor or unpublish the plugin which is causing the problem. I can't check it without an access to your back end.
I understand your concerns but problem 3 is not a problem with HikaShop, and problem 1 and 2 are new to me...
I'm doing my best to help you with the information and access I have.
The access you sent is not working. I got the error below when trying to login with them on your website:
Username and password do not match
Please double check it.