I’d like to ask you a question regarding the Qibla.

For almost all my life I have been praying in my home towards the south east direction (133SE) which to my knowledge was the correct direction.
Recently we recalculated it again for itmi’nan and it turned out that the actual direction was a little more to the east (117SE).

Now that I have corrected my direction, what do I do in regard to my previous prayers?

If your direction was within 90 degrees of the actual Qiblah then your previous prayers are all valid. Given that you were only 16 degrees off, your previous prayers are valid.