Hmm, not sure what is going on with your resizing issue. As long as the actual video file height and width match those in the web window html.index. <video> tag and the size of web window in Lectora there should be no issue. Just make sure the actual video is the size you want the web window in Lectora to be. Boy, that sounds confusing, I hope I explained it sufficiently.
By the way, the Auto play property will work just fine once it’s uploaded to your server. It wont work locally. If you do a lot of custom work I strongly suggest you set up a local server, such as WAMP on your authoring computer so you can see exactly how your work will function on a real server. Okay, I’m going off on a tangent. Time to refocus.
In the sample I attached, because I was not attaching the action to anything, I added a group and put the action in the group. I could have called the action directly (action299 in my sample) however, I decided to call the group (og290 in my sample) instead. I could have placed any number of actions in that group. By the way, the Lectora awt is in the zip as well.
Good luck and I hope this helps.