The first one is intended. The activity and the media are tightly integrated. You delete the media, the activity gets deleted and vice versa.
The second, we haven't noticed. You could have posted in the support forum with the link. I'm saying so especially because Delete option is the activities delete straight from BuddyPress and BuddyPress Media doesn't even add anything for deleting except filtering the activity delete so that we can delete the media with it.
Third, if you had noticed the discussions and/or contacted us, you'd have know that the next version, due in a day or two will provide a lightbox with navigation.
However, instead you chose to give us a very strong one-sided review that doesn't help anyone.
You don't want to look at this plugin, any longer. Accepted. You are not using or likely to use this free, open source plugin anyway. Then, why bother sullying the work of the developers and the thousands of users who've been patiently and diligently weeding out problems?
Thanks, but no thanks for your feedback.