it just so happens i'll hiking the exact timeframe as you. in sept 14 out sept 19. here's the sites i'm staying at
18 h49 (in 6 years i've never been able to book h48, so hard)
day 3 will be a hump, but i've done the trail in 4 days (death march), so it shouldn't be too bad.
as for you questions. pretty much forget about any cell phone reception. i highly recommend a gps in addition to your map and compass, it helps, particularly between hansen township and silver peak where the cairns can be confusing (over the years people build their own, without realizing they leading hikers astray). stay to the southern part of the ridge. the gps helps though, as if you need to backtrack you can be sure to not be lead astray by the same incorrectly place cairn again. it's possible to camp off-site, however, it depends on which section of the trail your on. let me know which day you concerned about making you site and i'll see if i can assist (i've hiked the trail 5 times, so I'm familiar with the layout). it can be tricky to find wood in some of the rocky sections, but generally you head a back into wooded areas even in these section periodically, so your bushbuddy may be fine. i still just use my msr pocker rocket.
also indespesnible are hiking poles and good boots (soft rubber for traction, as the rocks can be very slippery when wet). you probably know this, but just to be safe.
there's a tonne of views (i like the view before decsending moose pass near h23). the hansen township section is in my opinion one of the tougher parts to hike, but one of the most scenic there's silver peak, but given you doing the trail in 6 days, it might be a bit much to make up (depends on your pack weight, fitness level, timing, and sanity). it can take 3hrs just to hike up and back and the closest campsites are 1.5 hrs either way. you may want to skip it, unless you're willing to add another day, or you don't you don't mind hiking in the dark. plus, you won't be dissappointed by the other views, and it gives you something to go back for antoher hike.
hope this helps.