Welcome.
Have you turned in a Work Unit yet? You don't show up in the stats until you've completed and returned a WU. Stanford's stats page updates at the top of every hour, while the third-party stats pages update every 3 hours. One thing to note is that a WU returned too close to an update might not make it into that update; a WU received at 8:58 pm probably won't show up on the 9 pm Stanford update, but should be in the 10 pm one.
21k PPD would actually get you the full 10 Bucks every month assuming you folded 24/7; currently it's 250k points per month for the first 5 Bucks and another 250k (so 500k total) for the second 5. They haven't announced what the point levels will be for next year, which for EVGA's purposes starts in March, so those levels could rise in a few weeks.
If you haven't done so, you should get a
passkey. The PPD that the current public release of the client estimates assumes that you have one; the next public release will only do so if there's a valid passkey detected. All CPU WUs, and some GPU WUs, use a Quick Return Bonus point scheme where a good deal of the points earned are based on how fast a WU is returned. You need a passkey to earn the bonus, and you need to complete 10 bonus-eligible WUs to start earning a bonus.
The GT 640 isn't a particularly powerful card, but the PPD will also be affected by what core is running. The core is what does the actual calculations, and there are several of them. On the Nvidia end of things, there are currently two cores in use, core 15 and core 17. Core 17, introduced a little under a year ago, is newer and runs particularly fast on Kepler cards; a quick google search found someone reporting 23k PPD on a 640, and on high-end Keplers the PPD can be in the hundreds of thousands. Core 15 is the old core and is both slower than core 17 and earns less PPD because it's not as capable as core 17. My guess is you're running core 15 WUs right now; if the WU you're running is not from project 8900 or 9401, then you're using core 15. BTW core 17 uses the QRB, while core 15 does not.
Normally there's no way to specify which project or core to run (the ability to set a project preference is in the client but hasn't been implemented in Stanford's work servers), but by some server quirks there is a way to all but guarantee core 17 WUs;
this is a step-by-step guide. You're not really supposed to be running the beta flag if you're not a beta team member, so you won't get any official support if you do, but other than that they don't care much. They certainly won't kick you out or anything. There are many members here who can help with issues.
No one minds if you're not running EVGA parts; part of the Bucks program is to make sure that you will be in the future.
70-75C is warm, but not dangerously so. Most GPUs are designed to get up to 100-105C without failing, though I try to keep mine under 90C.