How to infuse vanilla into bourbon (or other spices into liquor) using low heat without reducing alcohol proof?

I want to make and serve a vanilla bourbon, so I want to maintain as much of the alcohol as possible--ideally all of it. I've tried nitrous and room temperature infusions with various amounts of vanilla and over various amounts of time. The flavor isn't as strong as I'd like in the amount of time I'd like. (I'm using just the beans and no sheath because the sheath is lending a tobacco like flavor I don't want.) So I was thinking to try heat to get a stronger flavor faster as I've gotten more pronounced vanilla flavors in shorter time when baking it into desert sauces. I figured that if I add the vanilla beans into the bourbon and heat it on low (below 174 degrees F, the boiling point of alcohol), let that go for x time (I'm thinking less than 10 minutes?), then I should maintain the proof? I tried in a large pot but it boiled at 150F, which I think may have been due to large surface area? I plan on then cooling the mix and letting it infuse for 3-5 days at room temperature (and then compare to the ones I infused at room temperature without any heat). It may be just this simple, but I'm getting a lot of mixed input on the internet.

I was also thinking that if it is reduced significantly, perhaps I could just add the infused mixture into straight bourbon to bring the proof back up. (Note, I have seen the USDA TABLE OF NUTRIENT RETENTION FACTORS but since this deals with cooking alcohol into food rather than on its own, I figured it may be different.)

(I have also heard of people using sous vide for infusing liquor with heat, but I don't really have those supplies at my disposal). If all else fails, perhaps I will just make a vanilla extract from scratch using bourbon and then use that, but it may be too aggressive.)