Good to hear that the phone hasn't been turned into a projectile yet.
The number after the ROM Name is the build number of that version of Windows. There are changes made with each build number, though I'd wager most of them are unnoticeable so better to just get the latest one. The idea behind these ROMs is that they are like a blank slate; they include the essentials but leave lots of free memory available for your own programs. Another advantage is that you don't have the overlap of having two different programs for certain functions like the default software, for example, there are two contact managers, one built in and another from Samsung. The 6.5 contact manager and most of those apps are more finger friendly which is great.
Clock/date thing is taken care of by the Titanium interface that I put in a screenshot in a post up above somewhere. Each ROM may come with a slightly different setup with different panels, but the clock will definitely be there. It's very clean, has big fonts and is easy to use. Alarms are built in, I believe they're similar to 6.1's but may be improved. I don't use them because I have no need for an alarm on my phone. Countdown timer could be handled by
G-Watch, may have been suggested before. That would require a separate install.
WiFi connection status is shown by its own icon (don't know how to describe it) that as I said before, will take precedence over the EVDO connection. Cellular data is shown when the cell tower icon changes to two arrows. Battery shows up at the top too, and tapping it will bring up a more precise meter.
It's unfortunate that 6.5 is being killed off and, as you say, why they couldn't enhance the UI anymore. Once you get on these new ROMs, you will see where they have made significant improvements, which I love, but it's a shame because I know they could have done a lot more to breathe life into this aging platform based on the enhancements they've already made, but once Windows Phone 7 is out, it's basically game over for WM6.
When you're ready to flash, I would try
this ROM if you haven't installed the latest Samsung software update - DC22. I used this one in the past but switched because it wasn't being updated regularly, now it is. If you need a guide to flashing, go
here and like always, ask back here if you've got any questions.