Can't throw out all that precious DT as I know how much you have probably spent.
Amazing how 3 of us within 150km's of each other have had similar experiences with the stuff and agree that once the layers build up or get too thick the $#%t hits the fan so to speak.
Only thing I can suggest is limiting it to 3 coats of each and just be thankful with the colour achieved or risk the chances of stuffing things up. Each time I went 'just one more coat' it ended up being one too many.
Kudos for your perseverance and patience and hope you have saved enough of the finish to work with and achieve a result you are ultimately happy with.