Usually the split first name is filled into the DS160 without spaces. For example Jai Shankar Patel becomes Jaishankar Patel. This way you are not omitting information. Also note that the second part of split first name ‘shankar’ must not be used as a middle name. I have also seen some people use ‘hyphen’ or ‘period’ as character but not sure if that still works.
Well, my first name has a space just like your spouse’s and I always used space and it worked in the past. Not sure, if that is a bug or a recent change. Just now, I even checked my online travel history on.Gov Website as described at : How to Check Your US Travel History, I-94: Screenshots [2022], still it accepted spaces…I think it is a bug, call customer service and clarify.