Hi Orion,
You're on the right track. Just reduce the same values slightly again, perhaps by about 0.5 on each.
The gaps in the tailpipe when viewed from the "outside" are a texturing bug in the model. The modeller hasn't textured both sides of the inner part of the jet pipe. Typically that makes parts of a model transparent when viewed from the untextured side. It's a problem that can't be corrected by the end user, I'm afraid. I think the developer sorted it when they went on to develop the (payware) CaptainSim version.
You ask about other anomalies...I'm not seeing evidence of the inner burner ring effect that's further inside the tailpipe (it usually has a blueish tinge) but that may not be so much of a problem. Your pictures are actually looking quite good as it is. Just a tiny reduction more in those Scale values.
The effect may appear very slightly further inside the tailpipe because you're reducing the diameter of the effect but, from your pictures, it's not looking too noticeable.