that's a hard one. how to get accurate data for our body using tools that introduce changes we don't want? I don't know how far along the research is on those videos or just pictures of the head/ears and some software tries to build the correct acoustic model. last AES stuff I read on this are a few years old already, and the simplified models seemed to consistently get too bright for the listener. Super X-FI is the obvious actual product that comes to mind, as they use pictures of the face and ears. but I didn't try and don't know much about it(knowing that the Realiser A16 would one day come to me, I've stopped purchasing all the little gizmos related to "3D" audio). I'm afraid it's creating a multichannel "surround" sound no matter what we feed it, I hope I'm wrong and it at least gives a choice. I guess if you could measure the signal really in your ear canal and then at a very similar position do just a speaker measurement(without you). the variation in FR could be fairly accurate and you could decide to only use that variation for your simulation. to remove most reverb, if your room isn't too small and you set it up not to have desk reflections right away or something, I guess you could just shorten the impulse and remove the trail of reverb(some reverb plugins let you play with that, but IDK if that's something you find in typical convolvers? I've stuck to free stuff so again I'm not very knowledgeable on what exists. I kind of butchered my impulses "by hand" like a monster when I made my own sauce a few years ago. or you can go the crossfeed way and just use the FR variations(or whatever you're comfortable with as FR alteration) and the interaural delay you measure between your impulses. or just the delay that makes you feel like a left channel only is at about 30° when you turn it ON and OFF. that way you have effectively removed almost all components of the room. 250ms should be typo. you typically would get something in the ballpark of 250µs (modulo head size and crap). if the app doesn't allow such fine tuning, you can consider just editing the .wav files by counting the number of samples or something like that. there is probably a way to export from REW without the impulse being centered on the peak, but I don't know how. I'm really a noob for everything beyond FR in that app.