Tack or Training?

I am having my trainer check my saddle fit tomorrow.  I'm concerned that it's causing problems.  I have watched every video I could find, read every article and scoured the internet for saddle fit, but I still can't tell if the saddle fits.  Yes, I can slide my fingers underneath the panel in front.  But how easy is easy?  How tight is tight?  How much pressure is too much?  Or not enough?  Too many questions.

The other problem is the symptom list.  It looks like this:

Biting when you touch her girth area (even with a soft brush or your hand)
Tail swishing, biting, backing up in crossties when you saddle her (also when you are just pudding saddle pads on)
Gnashing of teeth, swishing of tail, attempting to bite when I tighten the girth in the cross ties.  And by tighten, I mean the girth is so loose I could probably pick the saddle up over her head to take it off.
Circling defensively when tightening the girth in the aisle or the arena.
Resistant and crabby about going forward.
Hopping into the trot
Hollow back, swishing tail.

Yep, that screams saddle fit right?  Sure....except that these are also EXACTLY the same symptoms you would get for a horse who is trying to dominate it's owner and get out of work.  My pony is green (under saddle consistently now for 6 months) and smart and just doesn't feel like working.

Trainer #1 did not have the under saddle problems when she was riding her, but she was also using her own saddle.  Even with her own saddles, the pony still had all of the same problems with saddling..just not the forward issues under saddle.  There's a part of me that hopes the problems ARE due to saddle fit (look!  I'm not as incompetent as I think!  It was her saddle!!!) and another part that equally hopes that the problems ARE NOT from her saddle (I CANNOT AFFORD ANY MORE EXPENSIVE ITEMS FOR THIS PONY UNTIL NEXT YEAR!!!!).

Murphy's Law says that it will be the saddle because we're kind of out of money.  I mean, we have enough for emergencies and care but since the pony has had six months of full time training, an expensive round of ulcer treatments and a whole new wardrobe we just are out of money on the spreadsheet column marked PONY.

Problem #2 is the bit or the bit placement.  Or it's me.  I'm hesitant to show pictures because they freak me out.  It looks like my pony is being yanked on, even when there is NO pressure on the reins.  I'm going to be brave and post these pictures because I value y'all's opinions.  Before you jump in and say that she's fighting the nose band, her cavesson is so loose I can get at least two fingers under it, usually three.  It's so loose that Trainer #2 suggested I might try to tighten it so she can't evade through her jaw.  I'm not sure how I feel about that so I've left it loose.  Also, Trainer #1 (the one who rode her for six months) ALWAYS used a flash and rides her in a KK loose ring bit, not the Happy Mouth Mullen that she's in here.  So, be gentle with me but please check in and tell me what you think.

p.s. She's in the Happy Mouth because it encourages her to lean and take up the bit because she was SO far behind the bit when I bought her.  I have tried her in a Boucher, an O Ring snaffle, Full Cheek snaffle and finally the Happy Mouth.

p.p.s. I had to make the pictures larger so you could actually SEE her mouth.  She does have a long mouth which you can see in other photos where Trainer #1 is riding her, but she uses a flash so I haven't seen the grimacing before.

 I am adjusting her forelock for maximum pretty, but doesn't this bit look like it's WAY too far back in her mouth??

Not much tension on the reins, though I had just asked her to bring her head down with my legs.  Is she chewing on the bit because it's a plastic Mullen Mouth?  Or to show her unhappiness?

 Seriously, we're just standing here.  What is this face!!!!!??????  We could play a vampire pony in this picture

 Here it's better and I probably have the most contact out of all of the pictures.

And here she is BEFORE I rode, having an mini meltdown on the lungeline.  Obviously, nothing is messing with her mouth here and in fact when she is on the lunge she does not grimace.