> 1. I launch my beloved Interbase Windows SQL and click on
> "File"/"Connect to database"
>
> I can choose a remote database only (the "local engine" checkbox is
> disabled).
>
> Is there a way to connect to a local database using this tool ?

WISQL checks whether InterBase (not Firebird) server is running locally;
if not, Local engine is grayed out.
Just connect to Remote server, and use "localhost" as your server name
(using tcp/ip).
The drawback of WISQL is that it connects using Dialect-1 only.

Ivan
http://www.volny.cz/iprenosil/interbase/