1/ How can i do to remove the space between the top of the swf and the
thumbnails ?

i got a workaround for that problem.
my problem was, that i needed space under the big picture to display my caption text. the big picture is always in the middle and because of that the space over the big picture did also grow.
you cant change it with the "normal" simpelviewer version. but a "dirty trick" came to my mind after hours of trying to fix my galleries.

i had a html text and wanted the swf to start only a few pixels under it. but with the default way it was easily 50 or 70 pixals below the text.

i defined a div for the text and gave it some CSS format.
the important formats for me were:
margin-bottom:-40px;
position: relative;

the negative margin forces the next object below the text to be displayed higher than it usually would be. and that is the swf in my case.
in combination with a transparent swf background it works awesome.

good luck trying it :)