For better or worse the bars per minute expression of tempo is AFAIK universally used within the ballroom dance community. There are arguments for and against both methods, and both can be confusing in some cases. The abbreviation bpm leads to even more confusion but provided both parties in a conversation understand the system in use then either method can be used as best fits the users requirements.
Regarding your tune, I count it slightly faster than you (around 160) and would make it a slow Viennese waltz which would be useful at a social dance.
Your statement that 6/4 is double waltz timing of 3/4 may be mathematically correct, but that does not allow for beat emphasis.
I think it would be almost impossible to dance a conventional ballroom waltz to that music. Simplistically, you would need to step on beats 1, 3 and 5 of each six count bar to be able to waltz at half speed. However the music has a heavy emphasis on beats 1 and 4 which most mere mortals would be hard pressed to avoid.
Given that the third step of many basic waltz figures is a closing step there is often a tendency to shorten the time taken for this step. Add that factor to this music and my guess is that most people would dance three steps, each of different beat lengths, stepping on beats 1(23) 4(5) and 6. Three steps per bar, but not a waltz.