I am not sure what relevance being the 'main fee earner' has on the question, so I will skip over that part for now, but let me know if you had a question about it that I may have missed.
What was the restraint area of the contract? Are you engaged in conduct which was prohibited by the restraint of trade clause? What was the period of the clause? Restraint of trade clauses between employers/employees are notoriously tricky, particularly from the POV of the employer, they need to ensure they do not 'overcompensate' by restricting too much for too long in too broad of an area.
The Superannuation issue wouldn't have much bearing on this issue, all breaches entitle the innocent party to damages, but not all breaches entitle the innocent party to terminate the contract. In any event, even if you were entitled to terminate the contract for not paying superannuation you must 1. elect to the termination because of the breach and 2. If you proceed as though you won't terminate, then you cannot later terminate (so if you knew about it and didn't do anything, then you lost your chance to terminate).