First, screw your SA for not being professional. He should know and he should kautim the transfer.
Yes you can, call etiqa asap to cancel the old policy and transfer the 55% to your new car.
The waste time part is let say you only find out this problem 2 months later after the new policy enforced, you can only get the ncb on the remaining 10months. The another problem is when your insurance expires 10 months later, the date of the next level ncb still not yet completed 1 year.
But since you already achieved the max ncb 55%, so you are not affected by the insurance expiry date and yearly ncb increment date differences.

Your NCB will diminish every year if you don't use it. Nowadays few companies are selling only 3rd party coverage but you can try. They usually insist on putting in fire and theft insurance which bumps up the premium. You should use your NCD. At any time when you buy a new car your NCD can be transferred to your new car. You just pay full insurance for your old car for the unused time. For example if your old car's insurance still has 5 months to go, you top up for full insurance without NCD for 5 months.

Not sure about the latest rules but many years ago, I'd few car policies all 55%. When I sold one of my cars, I would still renew the 55% policy under 3rd party even though the car ownership had been transferred to the new owner. The only reason of renewing it is to keep the 55% NCB incase I want to buy a new car in the future. Those day insurance cover not linked to JPJ and 3rd party was cheap and manually issued.  Now e-cover note linked to JPJ, 3rd party cover also not cheap with minimum premium, can't play this trick anymore.
Since your car is not sold, I believe the 55% will stay regardless of 3rd party cover or comprehensive cover. Only when you stop the renewal entirely, the % of NCB will reverse at the rate similar to that of you earned the NCB annually.

I think 3rd party premium also not cheap, the NCB is useless in 3rd party cover because there is a min premium requirement. Have you compare the premium between the 3rd party and a min sum insured comprehensive cover ?