I not playing on Nutaku anymore, so my answer is no more than brief.
You can pass it and wait for currently active Nutaku player to answer.

- In term of stat Full bloom lvl 80 gold girls is strong as full evol lvl 70 rainbow girl.
Full bloom lvl 80 rainbow girl is just out of chart.
In term of passive skill you girls will get new passive skill / old passive get power-up by blooming them.
So if you can afford bloom any girl you have please do.

- You can choose the most strongest team with any type you have to challenge whale campaign.
Normally if your first group strong enough they should take care all deck fight easy.
So just change the girl in lowest group to match ship type you want.
But beware of your ship total power, if its too low than recommend your ship will be almost guarantee sink.

- I can't answer about personel equipment.

- 2nd affection make your girls more stronger about 50% not sure.
If you can afford please give it to them.

- I can't answer about crystal.

Right now Nutaku have daily deal that provide lots of thing.
I'm surely they will (or maybe already) sell bloom mats and 2nd affection item with this deal.
So it maybe easy to bloom and give 2nd affection to any of your girls in long run.
Sure if you willing to buy.