I assume these are ex vivo data? In which case, I’d recommend having a look through this recent post on the issue.
In general, your results do look quite noisy, can you post some example raw DWI images screenshots so we can get a feel for the data? Also, are you using dwidenoise on these data? If not, it would definitely be worth thinking about (along with mrdegibbs to remove Gibbs ringing artefacts).
Also, it may help to try to use multi-tissue CSD. Give dwi2response dhollander a go, and if that works, try a WM + GM 2-tissue CSD, using dwi2fod with the msmt_csd algorithm (this assumes you have no signal from CSF).