Frankly speaking I have no idea how you reached that 1200 points per 100 stamina in your calculations hehe .
You get probably 95 on average in 35 stamina maps, but that is 3 runs per bonus stage and end result of 885 points per 105 stamina, so not really better.
And there is a hidden error in my calculations in post above. I divided 1620 stamina needed after passive regeneration by 6.(3) multiplayer, but with such high stamina caps and 16h day cycle, you have only 8h left to regenerate while sleeping - that limits us to 160 stamina for night and not full cap, which cuts the multiplayer. Proper way should be then 1938 stamina minus whole day of regeneration a.k.a. 480. This leaves us with 1458 stamina to be divided by 5.(3) magma only multiplayer. And our end result is 273.4 stamina per magas refill, assuming you get +1 to stamina bar per each level up, with 81 max stamina I have on 37 level, you would need to be 230 level to be able to do this event with 160 magas burned on the way.
Frankly without magas its impossible to do. With 480 stamina per day and few level ups you would reach maybe up to 16k stamina over the whole event. 500k/16k = 31.25 points per stamina needed, or 3125 points per 100 - so as long as bonus stages don't give nearly 3k or 5 times more they give now, you wont be able to do this event without money/stored magas.
With level/cap like mine and 400 stamina average per day I have 12k stamina to spent over the event. With the 8.6 points per stamina based on your average values, I can reach up to 103k points without spending magas and not really much better if I used the few magas I have. So I should be able to reach to the second girl. But that is it.