001,
First of all, get good advice from your union!
But have you recently tried speaking to this captain 'mano-a-mano' (no gender implications!) - in a non-threatening and open manner?
If not, you may wish to consider this option before doing anything else. I say this, as going down the CAA/FAA/ASR/MOR etc route is fraught with problems - not least of which is that you depend on your current chief pilot (whom you will be openly criticising) for your continued employment and eventually command assessment. If you get known as a trouble-maker, your position gets awkward. (Been there, done that!) However, your conscience might dictate that you do have to take it further, as the risk of saying nothing and then this captain killing a plane load of passengers, would not be pleasant knowledge with which to live.
If you get to speak to the capt in question, apologise for going behind his/her back directly to the Chief Pilot but also mention your genuine safety concerns and the collection of evidence (once you have other FO's and CCs statements). Then ask him (politely) to desist from his inexplicable control inputs - if only for a/c structural-integrity reasons. However, firmly and calmly state that if he continues in his ways, then you (and others) will be left with no alternative but to take it outside the company. (Assertive behaviour in practice?) A witness to this conversation might be a good idea - the union might help here - especially if they represent the captain too?
I don't wish to pre-judge this captain but you may get nowhere with this approach but it is far less contfrontational and gives him a way out - a win-win situation for both parties and, at least, you will have tried. This will be in your favour, especially if it gets nasty later. However, if you do go this far, you might want to start quietly looking for alternative employment as the chief pilot (and possibly the captain) may have friends in the training dept who can ensure your life is a misery and command will become but a dream in your present company.
Failing that, the crash axe also get my vote!
Good Luck
flipster