problems with the tweaking of profiles (for directory)

hi all,

thanks a lot for drupal and all your efforts! since quite some time I
play around wit drupal and use it as it comes. thanks to the easy
handling of drupal!

this was sufficient up to now. however, for a upcoming project I have
the feel that my average drupal knowledge is not sufficient and i
have also to work with the profiles the first time.

i would like to establish a database for organisations (6000+) were
they enter themselves. i guess, this can easily done with the
profiles. however, I have the feeling that it is quite limited when I
would like to use the data and make it searchable.

problems i encountered so far are...

1* how can I make the "list selection"-field open for multiple and not
single choice (without creating conflict)? therewith organisations
can chose out of a number of predefined fields in which they work.

2* how can I make a search single profile fields (that people can
chose which field to search in)? can this be done with a simple
search extension? It should also be possible then to e.g. combine
search in two fields (or more)... e.g. that you can search the aims
or activities of the organisations only.

3* and how suitable are the profile fields are in regard to use
of the entered data for other and further proposes (e.g. use the data
for a directory in book form)? what should i take care of?

i hope this is the right place to post this questions and somebody
knows how to handle those issues... thanks a lot in advance!

best regards,
mohamed