I would use 'That's how' in conversation and 'In this way' in writing:
In this way his father helped him to get the job.In a 19th-century text, maybe a translation of a Grimm fairy tale or an Arthurian legend, something with deliberately elevated or (pseudo-)archaic language, you might indeed see a construction like (I'm making this up)
Thus did his father aid him in his quest.More examples on the web:
"thus did". But that sounds both literary and old-fashioned, so I'm not recommending it for the present day. If you use this construction, you need 'thus' rather than 'so,' but 'thus' in and of itself is rather elevated diction, so even 'Thus his father helped him,' though correct, is somewhat too formal in style for most modern purposes.
Peter {de} is right to point out that 'so' has a completely different function in your two sentences in post #5. However, in his second sentence, adding 'did' (without inversion) would have yet another function, namely, emphasis or contradiction:
So his father
did help him (after all) = Also sein Vater hat ihm doch geholfen