Monoxide,
had a look at your Tiff, there's no way to prevent core blow out with this as with your unstretched data, the core/ Trapezium stars are already way over exposed.
No manner of masking or processing will correct this. If it originally 'aint there, it 'aint there!
Your processing and colour with what you have is very good actually!
My suggestion is to go back, take shorter exposures so that the Trapizium stars are well defined in your sub exposures.
Process and composite the new subs, then go into PS and layer the new, shorter exposed composite with your original. Blending it till it looks natural. You'll probably have to have a play with curves, masking and feathering the Trap stars to find a pleasing stretch on the new image till it will match the area about the periphery of the core on the old.
It can be a difficult object to retain the Trap stars as well as show the surrounding nebulosity, including the Running Man Neb.
In the past I've opted for shorter exposures, retaining the Trap stars then doing a series of 'Zone' stretches, starting from selecting, feathering the core and working my way out. But I can be lazy at times.
But the simplest, and most effective way to go, and since you already have a good composite in your original would be to do the shorter exposed composite and layer.
It all takes a bit of messing till things look good.
A good excuse to mess around in PS.
BTW, I'm no Guru here, just what I've picked up.
Hope this helps and have fun
Rich
