I'm glad he's still doing okay.
Don't rush into anything.
First of all, do you have marine salt and a
refractometer now? Both are really important. I think you said 50L out of 190 were saltwater, which means the water has too little salt in the aquarium.
If you don't have them, call around to local pet stores and check if they have any. Many places that don't sell marine fish will still sell the equipment you need to keep your aquaria going.
When you say the filter is stinking, what does that mean? Does it smell like burning or is it just a "fishy" smell? If it's the fishy smell, that
should go away.
As for the source of the burning, I have one idea. What kind of lights does the unit have? Are they fluorescent or something else?