Hi,
I got your XML and checked it out.
What I could see:
1. The tags
<g:event_dateTime>
<g:from>2005-12-20T14:00:00
<g:to>2005-12-20T19:00:00</g:to>
</g:event_dateTime>
are not present in the XML file, so it is not possible that the error about the from tag is generated by HikaShop, it has to come from something else.
2. Shipping information and google category are not mandatory as far as I know so it shouldn't be a problem either.
Can you try to import that XML manually via your google merchant account ? What exact error messages do you get ?
If you don't have any blocking errors, if you activate again the automatic upload of the xml in the google product plugin, do you get any errors from the automatic imports ? If yes, what are they ?