What options do I have? Have I been unfairly or constructively…

What options do I have? Have I been 'unfairly or constructively' dismissed?
I am a sales mngr, I have been employed by the same company (in various entities) for 10+yrs. The business recently purchased by a private equity group, a name change occurred & a number of business changes have resulted. Most significantly my previous role was abolished (there was never any discussion, consideration or offer of a redundancy)& my role changed significantly to a field sales mngr leading a team of reps, I was required to 'hand hold' with on the job coaching, mentoring & presence with a different rep 4 days a week, the other day was filled with meetings etc. About 4 weeks ago I received an explicit email from one of my reps which I stupidly forwarded to 2 people outside of the org. 3 weeks later @ approx 1400 (following a call from my boss about 30 mins earlier) I was forwarded an email with a letter attached stating that I was required to attend a meeting at 0730 the next morning to answer a serious breach of computer & email network use, I was told that I could bring a representative but that I was required to notify who this person would be. The letter further stated that I would be given the opportunity to explain and that full consideration would be given to my response before a decision was made. The matter being serious may result in disciplinary action which may include termination of employment. It further stated that the policies could be found on the intranet. Despite my extensive search I was able locate the email policy but I was unable to locate the disciplinary or instant dismissal policy. I certainly was not trained in any aspect of these policies. Given the short notice of the meeting I was unable to arrange for a support person to accompany me to the meeting.
At the meeting I was presented with an email that showed an email trail with an attachment that was sent to me by my rep and me forwarding the email to 2 friends externally. There was no attachment produced by the company at the meeting. The meeting was attended by my boss (state mngr) and his boss (national sales director). No HR rep was present at the meeting. Given the email produced to me I agreed that the email had been sent by me. I was then asked to leave the room, so that HR could be consulted by phone. Approx 5mins later I was asked back into the room. I was advised that this is a serious breech & I was asked to resign or I would be terminated. I asked for clarity around the process, & was told that they had 'no where to go on policy'. At no stage was I provided with a copy of the policy. I was then asked to leave the room and formally resign immediately. After about 10 minutes I presented a letter of resignation. I was again asked to leave the room again, again HR was contacted and a letter of acceptance was forwarded to me after about 15 mins or so. I think that I may have been asked to sign the acceptance letter but I can't really remember as I was feeling shocked and overwhelmed by what had unfolded.
Since then I have been contacted by my boss via email and message bank, asking for my assistance with 'a couple of things that he forgot' so that I could help him to 'close these off'. These included providing him with various passwords and completing an update re my team members. I provided passwords but haven’t responded to his other requests or messages.
My termination pay was incorrectly calculated, after querying this, a mistake of approx 2k was identified. I have left behind a large sick leave balance.
My boss prevented me from obtaining my last bonus citing performance despite my team being the only team in the state that met target. Until a recent interim performance discussion (where I admitted not enjoying the role), no Performance Management has occurred, other than in relation to my reps & their territory. Since moving into my role, he has spent very little time in the field with me &/or my team. I received very little training, coaching or mentoring regarding the role. There has been no formal personal PM action raised in this regard. It is my belief that my manager has personal issues with me & I believe that I have been bullied & harassed since moving into this role. I understand that this is a very difficult case to bring.
Quarterly sales meetings are held &usually include a physical team activity as part of the program eg touch footy, bowls, 10 pin etc. Previously played a number of competitive sports & suffer ongoing knee problems. At the 2 most recent cycle meetings I have suffered from significant flare ups of my knees. My other half encouraged me to see my gp & lodge a workers compensation claim but as I had plenty of sick leave I thought it unnecessary. The last cycle meeting was in early February, I still have knee pain, am I still able to lodge a claim?