I suspect you mistaken here @mathepac , AFAIK and following some research, in concurrence with other posters it appears there is no process in place for penalty points to be awarded for the alleged offence(s) stated in the OP.If (once) summonses are served you will need a solicitor. You will almost certainly get points on your licence and a fine.
Yes, really. It's not just a non-display offence. OP signed a form declaring his vehicle off road and then used it while the declaration was in force. There was no tax disc and the vehicle was untaxed at the time of detection. That's three offences so far, and the most serious offence, which supercedes any safety considerations, is apparently attempting to deprive the State of revenue through a false declaration.
Penalty points, as I'm sure you know, are for breaches pertinent to road safety and while you may opine that the OP's offences 'supercede any safety considerations', it does not follow that penalty points will be incurred.
Good advice has been given here in that the OP should, as soon as possible, tax the car and pay all back tax due as well.
I know the OP said he has been summonsed already, but I very much doubt that, more than likely the guard took details and informed him that he would be reported with intention to prosecute. Wait and see if a summons or a fixed penalty arrive, but in the mean time get the tax in order.