I had just had a passing thought. We have a sweet cherry tree we have been planning to cut down as it is by itself and has showed disease symptoms pretty badly (it yellows and defoliates in late summer) and we haven’t really wanted to deal with the spraying sweet cherries would need in our climate, so no grafting other varieties onto it. BUT I wondered if it would be a possibility to graft weeping flowering cherry onto it (we have a tree of that). The only reason I considered it is that it is in our backyard and I could see our kids wanting to climb up on the lower limbs in a few years (we have mostly giant trees that couldn’t be climbed).
Sure you can graft flowering varieties such as ‘Kanzan’ onto the standard cherry rootstocks of mazzard (P.avium) and mahaleb (P.mahaleb.) For harsh winter climates… Prunus maackii is a great rootstock choice btw for anyone reading this.
I don’t know about the issues you’re already facing, but give it a shot.
Dax