Those are really good questions!
I would say:
1) Don't obsess too much about filling the freezer - enjoy the remaining time you have at home with your baby (rather than giving your baby to somebody else while you go and pump), and breastfeed your baby directly as much as possible to boost supply;
2) It depends on how well your baby takes to a bottle while you are away. While this is an unknown, just freeze small sizes. When your baby is taking a bottle well, then you can more confidently freeze larger amounts. Still advisable to freeze a mixture of amounts so that if your baby drinks 4oz and is still hungry, your helper doesn't have to spoil another 4oz bag which baby will probably not finish.
I never had much time to pump when I was at work, but I only went back to work after 6 months. I used to make sure I was as close to "empty" (your breasts are never completely empty) as possible when I left in the morning, by expressing from the other breast during feeding as Sarah describes, plus continuing expressing from both breasts after she had finished. When I returned in the evening, I would do the same, and these two expressing sessions alone would yield a huge amount of milk for me compared to the sessions I had at work when my baby was not around.
It varies so much from woman to woman as to how well your breasts respond to a pump when your baby is not around. Mine don't, whereas others seem to have floods of milk whenever they want. There are things you can do to aid letdown such as warm compresses (or just going for a brisk walk or climbing a few flights of steps first), massage, visualisation and relaxation.
Two things seem to help with pumping yield. Keep up your supply by breastfeeding as much as you can when you are home. If your baby sleeps well at night, you could try a "dreamfeed" when you go to bed, where you just pick him/her up asleep and put him/her to the breast. It might be tempting to pump at this time, but your supply will be better maintained by feeding directly (if it doesn't disturb your baby's sleep - every baby is different). Don't give bottles on the weekend. And stay confident about your milk supply. Easier said than done maybe. But if you notice a drop in your milk production, try not to panic - because worrying about your milk production is the surest way to guarantee a continued reduction in production!
Whatever happens, you will know you are doing the best you can for your baby.