Looks great Jim! Keep the pics coming... I have some walls coming up to do as well for a raised paver patio in back. Yours look great so far! What is the square footage of that drive going to be- it looks quite long.
Also, why the concrete block? I've done a number of segmental retaining walls and in all cases they don't need a traditional footing below frost line, but I've seen guys build walls with block below frostline if veneering with stone. It looks like you have a mix of CMU and SRW units? Not saying it's wrong as things are done differently everywhere depending on conditions, just curious is all...
...Problem is, when I pressure wash them, it pulls out all the material in between. Did I do something wrong to begin with or is it just accepted that you can't pressure wash a brick patio/driveway?
Polymeric sand. Get the good stuff (I used Techniseal, but there are a few out there). When dry it is super hard- can't leave an impression with a fingernail. When wet, it gets a bit softer, but won't wash out. I think a pressure washer might still dislodge it if you were agressive, but just to clean them it would probably be OK. One word of caution though- follow the instructions verbatim. If you wet it with some still on the surface you get a nice haze that is horrible to remove... but as Jim said- the patina is part of the character of pavers IMHO.
Also, no weeds and no ants moving around your sand. I pay about $22/bag for it with a commercial acct at a local supplier.