Probably impossible to reach quest 120 in the remaining few hours, this spec is rough...

I looked up how to get the Job Seed, and it seems you can get it from Mimic farming, daily missions, and the daily roulette, which makes it a pretty time-limited item... So, thinking you can reach 120 in the last few hours of the final day is a no-go, this is impossible. If you want to push hard in the final few hours of the last day, you'd need to be in the 'Hero Rank 15' by the day before to unlock your Job Level → then on the next day, maybe you can barely get 2 or more seeds from daily missions or Mimic farming (which probably takes several hours to get one?). So even on the day before, you might end up with just 2 seeds and fail to achieve the goal. Be careful~ (Advice from a defeated player)