Yep, no worries. But MSMT-CSD will be limited to 2 tissue types. To get 3 tissue types from such data, you’d need SS3T-CSD, which isn’t available publicly yet.
Sure, no worries again, but you may want to use the -fa option to dwi2response dhollander, and provide it with a slightly lower value than the default of 0.2. See this post, where success was shown on rat data: Multi-tissue CSD . The general advise for a mouse would be similar, but you’d probably have to be extra-careful about setting that parameter decently. Set it to a couple of values, and look at the -voxels output to see what makes sense (or doesn’t).