Hello, I hope the following assists you.
As the MIL was flashing to start with this would suggest a fault that the engine management has detected may cause damage, the light flashes to alert you to this.
By far the most common fault that causes this is a misfire caused by an ignition system failure, usually the ignition coil, a spark plug or H.T. lead. If a misfire is left then it can cause damage to the catalyst due to unburned fuel.
The poor performance and judder is due to the engine running on 3 cylinders instead of 4.
If possible check the spark plugs, remove them and check the electrodes for signs of burning and the porcelain insulation for any signs of electrical arcing along it. Check the output of the ignition coil, around 75% of the time the misfire is on cylinder 4, if there is no output on cylinder 4 but cylinder 1 is OK then replace the ignition coil, if cylinder 1 and 4 have no output or cylinders 2 and 3 together have no output then check the coil switching circuits.
Start with these points, let me know if you have further questions regarding this and I'll reply as soon as I'm able to.