Yes, you can adjust the image/slideshow sizes in functions.php - search for following code and adjust the height parameter as required:
$avia_config['imgSize']['widget'] = array('width'=>36, 'height'=>36); // small preview pics eg sidebar news
$avia_config['imgSize']['slider_thumb'] = array('width'=>70, 'height'=>50); // slideshow preview pics
$avia_config['imgSize']['fullsize'] = array('width'=>930, 'height'=>930, 'crop'=>false); // big images for lightbox and portfolio single entries
$avia_config['imgSize']['featured'] = array('width'=>990, 'height'=>400 ); // images for fullsize pages and fullsize slider
$avia_config['imgSize']['portfolio'] = array('width'=>495, 'height'=>400 ,'copy'=>'greyscale'); // images for portfolio entries (2,3 column)
$avia_config['imgSize']['portfolio_small'] = array('width'=>241, 'height'=>179 ,'copy'=>'greyscale'); // images for portfolio 4 columns
$avia_config['imgSize']['logo'] = array('width'=>446, 'height'=>218 ,'copy'=>'greyscale'); // images for dynamic logo/partner element
//dynamic columns
$avia_config['imgSize']['dynamic_1'] = array('width'=>446, 'height'=>150); // images for 2/4 (aka 1/2) dynamic portfolio columns when using 3 columns
$avia_config['imgSize']['dynamic_2'] = array('width'=>609, 'height'=>208); // images for 2/3 dynamic portfolio columns
$avia_config['imgSize']['dynamic_3'] = array('width'=>688, 'height'=>150); // images for 3/4 dynamic portfolio columns
Afterwards regenerate the images with: http://wordpress.org/extend/plugins/regenerate-thumbnails/
2) Can you post a link please. I need to investigate the button code with firebug.