I have answer for your first question.

I had same problem, one more member was displayed in the visitor info block.

The reason is that somewhere in the block the sql command count the anonymous user too while in the phpbb it will not be count.

I was using block-User_Info.php and after switching to
block-Site_Visitors.php problem was corrected.

you can d/l block-Site_Visitors.php from this site.