Why say havdala twice?

Yosey G. asked me to post this (it's relevant to Brachos 33a - everyone should feel free to post on previous dapim also. It's not limited to that day's daf. I'd prefer if we didn't got back too far but a week is definitely no problem).

The gemmorah tells us that although one made Havdalah in Maariv one is still obligated to repeat Havdalah over wine.

A few lines later in the Gemorrah quotes Rav Acha as saying that it is better to make Havdalah in Davening than over wine, but if one does BOTH he will get blessing on his head. The gemmorah questions this and says it seems from Rav Acha's words that one alone will suffice, if that is the case then why should he be blessed for saying Havdalah twice it should be an unneeded blessing and as such that should be a violation of LO SISSA! The gemorah retracts and says rather if he makes only ONE Havdalah it is better.

Now does Rav Acha argue with the gemora quoted above that said "although one made Havdalah in Maariv one is still obligated to repeat Havdalah over wine."? And even if he is, why does the gemmorah's problem of Lo sissa not apply to our accepted Psak which requires us to say Havdalah in davening and over wine? Also when the gemorrah changes Rav Acha's words all it says is that if one only made Havdalah once he should get many blessings. But that was just the end of Rav Acha's statement. How, according to this retraction would Rav Acha Start his statement? It seems his entire statement should be, one should say Havdalah in Davening and over wine, but if you only said it once than you should be blessed! Then why should
he say Havdalah twice?