It should be noted here that Hamas does not speak for the "official" leaders of the Palestinians.
From your linked story:
QUOTE
In a direct challenge to the Palestinian Authority, the Hamas leadership positioned itself in front of the group's logo and a green Islamic flag to send a message that they have the right to possess weapons and to claim responsibility for pushing Israel out of the Gaza Strip.
(Bold added for emphasis.)
1. Denounce Hamas; support the Palestinian Authority and Israel.
2. Other than offering moral support, as noted above, this must be settled by the people living there, or it will not be settled at all. The USA can do little but hope for the best.
3. I don't think so. Did anybody really expect Hamas to announce that it would give up fighting?