%w.att,? Total Damage % ? huh?

Sry to being ask again, accroding to Random_OVerlord: the rank given to best potential stat is

1) Total damage %
2) attack %
3) Stat %
4) Boss damage %.

question to be ask and re-confirm:

1. Total dmg% is the % derive from the damage range, example i had weapon that add 9% total dmg, my max atk range is 1000, after the effect, my max atk range will be 1090. (can be stack)
2. attack %, derive from total base weapen atk (include atk pot and atk apple, but not include bullet and star), (can be stack)
3. stat %, derive from the total stat after base stat+ mw stat. (can be stack)
4. boss dmg %, add up on skill %, example a skill deal 280% dmg, after this stat --> 280% + 30% = 310% dmg on boss. (cannot be stack)

question about potential skill:

1. how many skill is provided on potential system?
2. does each of the skill only available for certain rank of the EQ? (rare, epic, unique)

lastly, i'm playing hero and bm, any stat suggestion for this 2 class?