I do not 100% understand the pattern, if it exists.. I hope the native speakers of English could kindly elaborate on how to use this structure... The examples are:

1. It was me (or I?) who opened the file. - Именно я открыл файл.
2. It was he (or him?) who opened the file - Именно он открыл файл.
3. It is me (or I?) who opened the file - must translate the same: Именно я открыл файл.
4. It is he (or him?) who opened the file - must translate the same: Именно он открыл файл.
(is it OK to use 'is' in 3 and 4???)

5. It is me (or I?) who thinks about it all the time. - Does this structure make sense at all???

(if you are interested, we could discuss it via email or PM).. thanks, folks!