I wrote the reply quickly but to answer each of your questions.
1.  Yes you will get a vote that is worth 3000 SP or about 0.15 SBD
2.  If you upvote every post and your SBD amount exceeds 0.05 you will get a multiplier boost.  This is not a massive boost but serves to reward those that give more
3.  The multiplier increases daily, a fast investigation pointed to 8%, but if the community is happy with the system we will perform the math and release the finalised %, whatever it may be.

General comments:  The multiplier increases passively every day, it is qurator giving back some of the curation rewards obtained from using your SP and is permanent.  We expect the largest boost will come from delegations.

Also if you build up a multiplier with 300 SP and then increase to 400 SP, the multiplier will drop slightly, because the multiplier was built up using curation rewards from the 300 SP.  The reverse applies if you delegated 400 SP and decrease to 300 your multiplier will increase.  This is also to stop bad actors from building up a high multiplier by delegating 1 SP and later adding a 1000 SP.

The multiplier increases daily, but it will increase very slowly.  We have been playing with the finances and 8% per year looks to make financial sense.  The growth will really help long term delegators.  It is better to work with the base 10 multiplier in the short term.

There will be increases to the multiplier if you exceed the 0.05 SBD, but the lion share of increases will come from delegations