Thank You Scott,
that sounds good, I could work without related questions and as well without tags.
But the search I would need.
Regarding the work to change the recalculation: In qa-db-recalc.php are some functions which do fill the table qa_contentwords. I think it would be fully enough to only fill this table with words from question titles, just have no idea still how to get there... So I would have the possibility to search in titles at least.
About the space, this website wont have much income, it is more an informative site about 200.000 schools/locations, where people can comment some things. There wouldnt be additional schools (questions), just answers or comments.
I actually have qa_contentwords at about 530 MB, the shared hosting limits its databases to 1 GB.
However, having an option to choose if content or just titles are searched could be a nice feature for the future...