Got a name to go with the graph? Fair chance I've played with you
1. Yea, 2.5K games is a fair sample but obv > 2.5K is desirable.
2. I would recommend 15-20 buy-ins for your desired stake. Probably 15 buy-ins is best because those 6-max hypers are swingier than the 1960s - i.e. enough roll to survive an early downswing but not soooo much that you can lose a fortune in one sitting. So if you wanna play $15s next, I would want $200 min. Not to say you can't do it off 10 buy-ins (which is my usual cut-off) or even 5 buy-ins if you want to gamble a bit.
3. Personally I wouldn't back anybody other than myself in hypers and I haven't seen any other OH8 player get staked JUST for 6-max hypers.
I think you are making a tragic mistake if you believe hyper-turbo to be an acceptable form of poker. I'm a long-term winning player at hypers but you gotta make peace with the fact that this form of poker is as close to roulette as you ever wanna get. Many good players (as in top 10 SC players) have had gargantuan swings in these games and the BEST a relative newbie could ever hope for is an ROI somewhere between 3-10%. As far as I know, I have one of the best ROIs for a reg hyper-player (5% @ $15, 9% @ $30). I would recommend checking out the stats for wadzon, juicy_j_93, salisero, bokkie87, angribob, xQuantum1, to get a feel for what you might expect in the next levels.
The best advice I can offer is to stake YOURSELF in some 18-man turbo SnGs at $7, $15 and $30, alongside the hyper stakes you are currently playing. If you make some $s and are cool with the FACT that you might lose them ALL in one hyper session at higher stakes, regardless of how perfect, or otherwise, you happen to play, then sure, go for it and gl
Sorry if I seem pessimistic btw but I feel most hyper players are entirely ignorant of the game they play.