On a new event, it should default to your User Timezone (whatever you set that to)...The Calendar/Event  Module does not set it to the Portal or Server Timezone...this is because DNN does not normally expose the Server Timezone...only the Portal and User Timezones.  So, I guess what I'm saying is what you are saying the module is doing is impossible (at least according to the code I wrote).

I'm not sure what DNN set's, as a default, your User Timezone to, when you create a new User Account...what was your User Timezone set to?  This may be a bug in DNN...Hopefully new User Accounts are set to the Portal Timezone and not the Server Timezone....

Once set (on a new event), it will always be edited in that Timezone (unless you change it).  On a new event you can set the Timezone to whatever you need it to be...

1) not sure what you mean, "the event time is 3 hours behind"...on what form (month view, edit form, detail form)?  Currently while editing the time...the date/time is not edited in any way (whatever is keyed/selected -wysiwyg).  The timezone selected on the edit form is the selected timezone...when displaying the date/time, the date/time is adjusted from what is keyed to the User's (or Portal, if anonymous) Timezone.

2) "the end date is not updated"...are you referring to the duration end date, or the recurring end date?

The more specific you can be the better.  If you can email me screen shots, it would help (support@avanced.net)