A Few issues here.

Hi 

Gonna try and help a little. 

Let's go in order I suppose.  

1 and 4, The potion thing I can understand to be annoying but there are camps all around the map, so it shouldn't be that bad and of course you can have regen potion or healing mist in your other potion slot to make it a little easier on you.  As for using 8 potions for one fight I have to wonder what health your using them at.  Cause for me and I played on normal I ran around the entire map of hinterlands and maybe used two potions.  When I went to fight the dragon I only used 6 potions then.  So this might be because you have your party members set to taking them at half health, you could lower that to 25 percent or lower.  It might also be because your armor and weapons are too low level for you and you simply need to upgrade them.  On my first playthrough I had two of my party members use level 3 gear till they were level 8 and then I upgraded and I noticed the difference right away.  There is also an inquistion perk that adds another 4 potions, to give you a total of 12. 

2. The Astrariums may be a glitch, you could use the old work around of saving your game and then loading back in, that might help or if it's not a glitch and there are like three more stars or something, it's a challange.  Just try and you'll get it.  I found the astrariums rather easy.

3. I'm a little confused but I think I got it, changing from melee to ranged.  Umm well there are a number of ways.  if your a rogue you can buy a tactical renewal and change to either archery or duel daggers, mage you sort of have a way to be both with knight enchanter and warrior well your out of luck there.  Or you could do what every other dragon ager does from time to time, simply play as one of your companions when your out in the wilds.  Whenever I didn't feel like being a mage I would jump on Cassandra or Cole and play them and I simply did that by clicking on their icon on the left of the screen where their health is. As for the trunk that will probably be brought back in through a dlc or something, or I could be completely wrong on the trunk front, don't quote me.

5.  There is a game guide, it was released on the same day as the game.  Bioware probably didn't include it with the game probably because there are three different versions you could buy.  The ultimate guide, which included a lot of things (can't remember what), the collectors edition, (which I bought) and the regular edition that just included the book and nothing else. 

6.  Umm I'm not even gonna touch that. 

XoXo MockingJaye