I'm assuming you're upgrading Y->C, but C->F is mostly the same.
- Yes, No, Not sure. MP will be able to tell you how many miles are needed to upgrade LH flights. Keep in mind miles upgrades have limited fare buckets that they can be applied to. SWU's only have S & W which they cannot be applied to. I would guess 30k miles FRA-TLV, even though it is very short--LH recently reclassified TLV to be in the Middle East region rather than Europe where it was before.
- Again, not sure. I would guess less if you upgrade SFO-TLV than if you did SFO-FRA & FRA-TLV seperately.
- Hard to say of course. But if there is a free seat in C when they start boarding, then someonw (hopefully you) will be upgraded into it. Using miles on LH means you can confirm in advance, you just need to find Business Award seats on LH and then call MP. They'll issue you some paper certs which you surrender at check in.
SWU's are standby only but have a wider range of applicable fares. The LH DM list is only sorted by time of check in, so getting to the airport early helps a lot.