If I understood correctly you are rendering your deconvolved impulse response with a clap sound and exporting that as an impulse response?
If yes, then that’s your mistake.
You can use a sweep signal or a clap (balloon pop, runner’s start guns, film clapperboards) signals to excite the air inside a space, to get the space’s response, and then you deconvolve it, which means that you remove the signal that you used as exciter and you are left only with the space’s response.
That later is used in the process of convolution, that simply multiplies each sample from your sound stream with all the sample from the (deconvolved) impulse response, layering all multiplications by adding them as many buffers in time, and that produces your acoustic simulation output.
By adding an extra exciter (the extra clap in your case), you actually undo the deconvolving that you done in the first place, to remove the sweep signal exciter. So the convolver in FMOD works ok, but your sound is in fact (and you describe it perfectly) metallic or harsh. The tiny-fication you also report might be that the added clap adds to the gain and the convolver has to normalize even more to achieve its layering, so the volume goes lower than expected.
If you want to export the impulse response to a native wave file to use in other software (like FMOD), instead of adding a clap on your DAW, try adding an impulse, which is only one sample with full volume. This will also allow for your exported impulse responses to have a 1.0 factor as their 1st multiplication layer in the convolution process, which sometimes works nice in convolvers used as inserts (instead of auxiliary sends) with 100% wet settings.
Here, I made two impulse files for you: https://1drv.ms/u/s!AoFZ1MP3ewRggeVrcTRCVG3LmC2ceg?e=KmhFCG
One is 32 bit floating point, and because I don’t know which DAW/editor you use I also made one at 24 bit. I also added enough silence to make the samples 1 sec long, as some DAWs or editors have issues with files that have a duration of only one sample.
For games as @brett suggests, it’s better to optimized your exported impulse file. Anything around 44.KHz /16bit would be good. In FMOD, as the convolver doesn’t support resampling of the impulses to the project’s rate, you should decide early on for the sampling rate of your final project and use that sampling rate for the exporting of your impulses. Pro tip: Don’t use dithering on the exports, for impulse responses it will mess with the fidelity of your final outcome.
@brett, if you are referring to an impulse signal as the “click” in your recommendation above, I disagree that it would make for a good sharp sound as an exciter in this case, because @jessekirbs mentions that he wants to capture the response of an actual space. Impulse signals are excellent for capturing hardware processors or software plugins, but they cannot provide the power needed for actual rooms capture. For real spaces you need either loud bursts of noise as you need both power and full spectrum to capture the room’s full response. Some pop balloons or use film clapperboards, or even start guns used in running competitions, that provide a good ratio of full spectrum to power excitement for the room to react.
I will leave you with a final tip that I found working for me great for game audio through the years, either create a monophonic impulse response, or make sure that the stereo reverb isn’t create any clearly perceived positioning of any sound you pass through it outside the center. Game sounds come from various directions as the games pan sources in real time. You don’t want your impulse response to always balance constantly to the right or left of the image of your output. Balance your wet sound to give enough character of the space, and your dry to allow the players’ understand from where the sound is coming.
I hope I helped, stay safe!