You get one token for every 10 experience points (rounded down), so you would need somewhat more than 100,000 experience points in Dungeoneering to get 10,000 tokens. If you get some Dungeoneering experience from activities other than Dungeoneering (e.g. experience lamps, or the Tears of Guthix activity), that won't give you Dungeoneering points, so you would need more than 100,000 experience points total in this case.
You can only get dungeoneering tokens by getting experience in dungeoneering - that is, by completing dungeons, alone, or in teams of up to 5 people.
you get it from dungeoneering for 34k or 44k tokens
Rewards, at the Reward trader south of Daemoneim.
The highest level for all skills except Dungeoneering is 99. Dungeoneering can be trained up to level 120.
The best way to get tokens in dungeoneering is to get as much experience as you can on every dungeoneering floor. You get tokens from 10% of your total experience. For example, if you get 5,839 XP you will receive 583 tokens. Total experience depends on the floor XP and prestige. So make sure you raid the floors only once. After you've raided all available floors, reset your progress. You will also receive more XP when you raid floors in a party with other players. If you do raid in a party do not be a Leecher! A leecher is someone who just stand there and doesn't help the party.
Level 30 for now. As soon as more than 2 million players have Dungeoneering level 30, a higher level will be required.
If by Gravity Shortbow you mean the Gravite Shortbow, it's a reward bought from the Reward trader for 40,000 Dungeoneering tokens outside of Dungeoneering. It can't be brought into the dungeons and isn't an item in the dungeons.
The deepest level floor available to non-member RuneScape players is floor 35. Floor 35 can be accessed by players after reaching level 69 Dungeoneering (about 650,000 experience in Dungeoneering).
You need 40,000 Dungeoneering tokens, so you need to get about 400,000 Dungeoneering experience. I couldn't find any reference on how much experience you typically get per hour, and I don't have enough experience myself yet.
Depends on several factors: The number of players you are dungeoneering with. The complexity level you chose. How much of the dungeon you completed. And so on.
You can get prestige tokens by reaching level 80 and starting at level 1 again.
Yes, for everything except Dungeoneering (level 120)