Hello,
We are happy to hear that your kit work verry good for you.
About your first question, i didn't think that this is from low voltage. If you have low voltage your schematic will not work. Ucc must me around 3.5 volts or litle bit low. Better check your LED polarity and conection to pin 4 on IC or pin DAT, betwen DAT and GND led must light on. Try with multimeter diode tester. check soldering on pin 4 or soldering on resisitor R4.
About second question. This pins is for
ICSP programming, not for JTAG. Most programmers have ICSP connector.
http://en.wikipedia.org/wiki/In-circuit_serial_programmingIf you looking for cheap method for programming search in google for ISCP programmer for serial port.
I hope this helps.