I haven't read all your responses so I'll put in my 2 cents' worth. First of all, I can relate as I seem to be a bit itchy too. That's because it's really dry out in addition to the heavy Cedar Fever and the goo that is in the air.
For these things I use a couple quick combinations that help me not only topically, but internally. These are: 1) ingesting and also rubbing on my skin and hair virgin coconut oil. I also cook with it as well as with virgin olive oil. I might also recommend that you start eating some walnuts, since they have essential fatty acids and oils in them that help.
2) Try to increase your intake of water daily since this helps to hydrate and replenish your skin's water content and plumps up your pores.
3) Exfoliate your skin with sea salt compounds (try SoapRano's exfoliating salts) while in the shower. do this all over your body. Then when you get out, pat yourself damp, not dry. Follow up immediately with coconut oil.
4) When showering, use warm water, not hot as hot water will dry you out a little more readily. If you have to do a shot of hot water to be warm enough, follow that up with a cool shot of water just before you finish your shower to close your pores. This is also good for your scalp after shampooing and conditioning.
5) You say that you shampoo frequently due to the grease on your hair. You might try a hot oil treatment on your hair at least 1ce per week then shampoo it out. In between shampoos which could be as much as 3 days, you can let the sebum build up, since it coats the scalp. This will depend on how comfortable it is to you. As long as your hair is not greasy or smelly between shampoos, it might be good practice for the short term until your scalp gets normalized.
6) Aveda products (and many other products) may contain perfumes that may over time, irritate your scalp. If so (or you suspect they do), try another organic product that does not have much perfume and see if that helps. I have found that occasionally, I become more sensitive to shampoos and/or conditioners that have perfume in them. The other thing you might try is to reduce the amount of shampoo you use as you might have a little more residue, which can also irritate and cause your scalp to flake. I would not recommend using anti-dandruff shampoos since they just create a vicious cycle and do not rid you of dandruff, contrary to what they'd like you to believe...
For some quick relief, after shampooing and conditioning, you could use some Listerine or Mint based mouthwash on your hair, then immediately rinse it out. I can't tell you how refreshing that is, although I know it probably sounds wierd.
For remedial use, coconut oil on your hands and body daily works well and it's not greasy or sticky -- it soaks right in, which I like. Premise here is that if you can eat it, then it's going to be good for you to put on your body since your skin is the largest organ.
Good luck to you, Jen!