Hey Didier
To answer your questions:
1) The number used in brackets is taken from WordPress count – which is managed by WP itself – if for example in WP admin, you click on “categories” under “posts”, you will see a “count” number, this plugin uses that – so it doesn’t reflect/respect the current search preferences.
Search & Filter 2.0 will have this feature, which I was hoping to release at the end of this month however I’m a little behind on it.
2) How are you storing your prices? They must not have any text or currency symbols and must only be the number – otherwise you will get strange results.
Thanks