Ok, I just got back into archery with the idea of hunting, after several years of just playing around with my longbow.
I picked up an inexpensive compound bow as my starter but it is a heavier draw and speed set-up.

#1. The problem I'm having is finding arrows of sufficient stiffness for the weight heads I am looking to use.
I started out with Beaman ICS Hunter 340s, but I'm getting a LOT of fishtailing when using anything heavier than 85gr heads. 100gr works OK but still has some wobble. 125gr wags so much you can see it at 15 yards, let alone 50. I want to find a fairly stiff spine arrow to move up my point weight to something in a usable range. Everything I look at seems to top out in the 75lb or 80lb range when using 31" lengths so I have a feeling that I am maxing out the range of the arrows I have.
Add to that, I don't want to spend $$$$$$$ on arrows right now since I may be trying out a few types. I've had someone suggest Carbon Express Terminator Hunters 6075s, but don't want to fork out $50 for 6 just to experiment.

#2. How about vanes, Since I am using a shoot-thru, I have been told by one shop to use Blazer 2" vanes with a Helical, another said no, use Quick-spin set straight. What's is your experience with which will spin & stablize a fixed broadhead best?

Tech data. Bow is 75lb actual draw, 75% let-off, hard single cam, Shoot-thru rest, using a release. Arrow length is 31", though I could shorten up to 30" if needed.