1. Jesus has no role in Judaism whatsoever.
2. 1 to 3 (if Orthodox).
3. Jews believe that there were many prophets, including Moses, Isaiah, Jeremiah, and so on. They do not recognize Jesus or Muhammad as prophets. Elijah the prophet is supposed to return before the coming of the Messiah.
4. In orthodox synagogues, the prayers are completely in Hebrew. The Siddur (prayerbook) of an Orthodox synagogue will have Hebrew on one page and English on the facing page. In Conservative and Reform synagogues, there will be some Hebrew and some English. The more reform, the more English and less Hebrew! Also, it is called a synagogue, not technically a temple. The Temple refers to the one in Jerusalem which is not currently standing. Reform Jews do sometimes call their synagogue a Temple, but Orthodox Jews would never do so.
5. Yes. Of course, the 1st Christians were exactly that. They were Jewish people who believed Jesus was the Messiah, and they kept the Sabbath, Passover, and all the other holidays. Today, sometimes a Jewish person converts to Christianity, and a lot of times, a Jewish Convert to Christianity maintains an interest in their Jewish heritage, or for theological reasons believes that the holidays should still be kept. They are usually called "Messianic Jews."
6. No. I think most Orthodox Jews can probably at least read it. But even in an Orthodox synagogue, you'll find people who are far from being fluent in Hebrew. They may have memorized what the prayers mean, but wouldn't be able to go to Israel and just start speaking in modern Hebrew without further practice.
Hebrew is a beautiful language, a joy to learn, and enhances your knowledge of the Bible tremendously. I highly recommend it!
There is a great book by Hayyim Halevy Donin called "To Be A Jew" that I highly recommend. It gives the basics and is very well written. Another good one is "This is my God" by Herman Wouk.
There are some excellent Jewish websites. Some of my favorites are:
I recommend getting a Jewish Tanakh (Bible) - if you can find one with Jewish commentary, that'd be great. Start reading all you can. Visit a synagogue. Pray. God bless.