1. For desktops, you will have to live with having two audio formats. Sorry. It's the browser's fault.
In terms of mobile, you will be hard pressed to get even the simplest game to run at any decent framerate on iOS safari... No need to try to conform to this platfrom then, much better to use a wrapper (directcanvas or cocoonjs).
2. You will have to detect whether the user is using a mobile device, then change control schemes according to that. It would probably be better to export two different versions.
Basically, look into wrappers instead of using the device's browser. Unfortunately you will be very disappointed about performance in this regard if you choose not to use a wrapper.