The harp arpeggios on P. 5 are most certainly playable, although it would be very uncomfortable with one hand as it is written. Such passages are routinely divided up between the hands, and it's best if that is indicated in the score. While harpists are accustomed to rolling their eyes at the absurdities presented them on occasion, and they are also accustomed to marking the division themselves between the hands, still they will appreciate it if you don't ask them to do your work for you.

Best is to notate LH notes on the lower staff and RH notes on the upper staff. Beams that cross the staves are common.

On P. 6, it would seem to be better to notate the G-flat accidental as an F-sharp, for two reasons. First, the area has a G minor sound to it, and F-sharp is therefore the leading tone in that key. Also, when writing for harp you have to keep in mind that if a specific note has been sounded recently, you may get a buzz if you ask for a pedal change on that note while it is still sounding. Best of all is to sit down with a harpist and talk it out. There are general guidelines you can follow, but sometimes you can't know until you try it on the instrument.