I think the three and half inch look look the best.
I have wiped marks off with a damp cloth, but other than that I dont do anything else to clean them.
I dont know how to.
I once tried washing a sample length of fabric blind, and it came out matted looking, so I wouldnt recommend that.
They are like curtains,they look clean while they are up, and you dont see the dust until you take they down.
I dont take the blinds down, and they still look OK to me.
I was told to put them in a pillowcase ,and pop them in them washing machine but dont know weather to risk it , when they get realy dirty i may try it .