A couple of things to point out. (This may vary slightly based on splunk version)
I don't think you should ever have to mess with the etc/modules/... folder so I would recommend undoing any changes you made there.
To set the sourcetype, you should be able to simply set the "sourcetype" parameter in your input stanza. So your inputs.conf entry should look something like this:
sourcetype = syslog
I should point out that splunk does not recommend the usage of fifo anymore. So I would suggest either (1) use syslog-ng to write to files and have splunk pick up those files, this has the advantage of protecting you against losing events whenever splunkd is restarted, or (2) if short outages (due to restarts) are not a problem for you then you can configure splunk to listen on a TCP (or UDP) port and have syslog-ng forward your events to that port. (You would use the same sourcetype=syslog option for that input as well.)