That sounds like an ambitious project. Off the top of my head, it sounds doable. You’d have to generate a CSV file with your two tones, measure the amplitude and phase of the 3rd order responses (in a highly linear measurement system), and then subtract the 3rd order responses from your CSV file (or something similar). I would expect that you could drop your 3rd order intermod products by 20 dB at least, but you’d have to try it to know. And it would vary with temperature and frequency, so you would probably want to do it right before using it or after a 30 minute warmup. Assuming you want tones spaced 2 MHz (+/- 1 MHz) you’d want to choose a DAC clock that is a multiple of 6 * tone spacing. Something like 96 MHz would probably work nicely.
If you can’t get phase info, you could use the amplitude of the IM products and hunt for the right phase that exactly cancels the undesired IM products.
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