You can also adjust the reply box size by dragging the top grey bar of the reply box. This should adjust the ratio of reply to thread text on your screen:
To search within a thread, you can also use the site’s built-in search, at the top right corner. Clicking “Search This Topic” to contain the search to the current thread. For example:
Also note that the “Search This Topic” will automatically change to “Search [whatever] Category” if you’re on a general forum page.
Or “Search Posts by [member]” if you’re on their profile.