Roman Numerals specifically "I"
1. Could be 129 in all - With Roman Numerals, each unit (1, 2, ..., 9) is assigned a separate letter.
2. I stand alone and with others - I (alone), II, III, IV, V, VI, VII (with others)
3. I may have began my journey in Egypt- Hebrew numerals were first which were Egyptian. The system of ancient Egyptian numerals (later called Roman Numerals) was used in Ancient Egypt in around 3000 BC until the early first millennium AD.
4. I may be used interchangeably - See number 2 and I can be used in English alphabet to form words.
5. You can count with me - See number 2
6. It could be in a UNIT - See number 1 and 2
7. when I am small I look different than when I am big? I looks different than i
8. if I were me which I tend to be who am I? - I am me
9. All in All there is about a dozen or so of me in all my clues... - Lots of "I"s in your clues.
10. The answer is right in front of your eyes. - or "I"s
Tornadoes all around me/power on and off. Sorry for the edits.