When troubleshooting start simple and work your way up trying it at each step.
One thing that may be getting you is where you are entering the formula. If you just type today() into the default box it will treat it as text. Haxe you used the FX button and gone in and added a function and selected Today from the list? This should be pretty straightforward. Going through these steps I added a text field, opened properties, selected the FX next to default value, Insert Function, selected username. These would need to be seperate fields or you would need to use concat to join them together in one field.
For the web service may be a bit trickier to debug. I would create a test form with just your webservice data connection and instead of onload put all the fields on the form and query it manually to make sure it is performing properly and setup properly. Sometimes onload the data to use with it is not available yet due to timings unless it is a default value.