Thank you for your post.
It sounds like you have everything set up correctly. What occurs when you try to launch Admin Console? What occurs when you enter the IP Address into a browser?
Try the following:
Using FileMaker Pro, open one of the files that you want clients to access via Instant Web Publishing. Pull down the File menu and select "Sharing -> Instant Web Publishing...". Turn on Instant Web Publishing, select the file in the lower left quadrant, and in the lower right quadrant, set the Instant Web Publishing access to "All users". Click OK.
Close this file, and upload it to FileMaker Server. Open the file using the Admin Console. You should now see Instant Web Publishing enabled for this file.
Go to another machine, open a browser, and enter: http://<IP Address of server>/fmi/iwp
This should present the Instant Web Publishing page with the file being listed. Click on the file and open it.
Keep me updated with any progress.