In your time frame and with your wish list, I agree you will need to cut back if you are to enjoy this trip and do the things you want to do.

We're interested in the cafe/small bar scene, arts/culture/music (dare i say the hipster scene, sigh!), strolling around neighbourhoods rather than sightseeing' as such, so keen for places with a youthful vibe and food/drink scene rather than museums/history per se.
You may be better to stick to the eastern more compact State. Fly into NY or DC - mind you DC itself is one huge museum...... but one which should not be missed. You could then design yourself a tour with your wish list over the eastern States, which all have a lot to offer for what you want, especially if you get off the interstates, and use the older highways and local roads. There are so many lovely towns which would give you a sense of what you are looking for.

This way you would also be able to design a loop trip, and avoid that not insignificant fee for picking up a car on the west coast and drop it in the east of the country. These fees can run into many hundreds of dollars.

Whatever you do, do not compare a roadtrip in the US with anything you have done in Oz or in Europe. There simply is no comparison. In the west you can go for long distances, but if you want to see smaller towns, experience bars and cafes and stoll around neighbourhoods, in the 14 days you have, you will find a treasure trove of what you are looking for, without having to spend more than 50% sitting in the car. For a touch of grand nature, you could even add Niagara Falls. DC, Boston and NY are all 'walking' cities with good public transport.

Do you actually have good maps of the States? If you cannot get these locally, I highly recommend that you get yourself a Rand McNally road atlas.. You can order it from the RTA store via the link at the bottom of this page. If you order it now, you will have it in a couple of weeks. You can then research on the web those things of interest you will see on the maps.

You do not mention which State you are in, but if you are a member of RACV. NRMA, etc, then be sure to bring your membership with you. It will give you access to free tourism information from the AAA anywhere in the country.

And of course, bring a small flag to put in the back window of your car, to show who you are. Yanks go crazy over flags! :)

Lifey