I am also an engineer. While many of the attributes you and John28 mention are usual for engineers, especially senior engineers, there are others that work in your favor.
Ordinarrilly, we tend to be highly creative and are accostomed to thinking out of the box (assuming he was good at engineering). We are naturally inquisitive and are usually more interested in the how's and why's than most people. Also, it's been my experience that when presented by either evidence or a logical argument that our intended course is not going to be the BEST solution, we are typically quicker and more willing to adapt than the other proffesionals we work with.
Furthermore, our vanities tend to be tied to what we can accomplish with our minds and in the scope of our knowlege. I.e. We love to be asked to fix things. Especially when there's a tough problem to overcome.
Now, as to feelings, I am not a typical engineer. I don't hide mine behind a wall. And like John28, am a decent communicator. If your H is not gifted in these ways it might make it tougher to judge your progress. But that doesn't mean it's Impossible.
If you can get him interested in overcoming obsticles together, however mundane, it will probably piqué his interest. This is probably why he's noticing your changes and is curious about them. Keep working and stay open to different things. Be prepered to keep him guessing and playing mental gymnastics. He might start enjoying the challenge offiguring the new you out.
Don't get me wrong, it might not go the way you want, but there's a chance that you become more attractive to him by keeping his mind active and little by little, he loses his interest in D because there is a better solution right in front of him. At least, in the mean time, you are working on you and either way, you end up better and stronger for it.
Good luck.
ADAPT. OVERCOME. IMPROVISE. -Tom Highway
Me: 43 W: 40 S12 & S9 Married 17yrs Together 20yrs