“Lilac witches' broom is caused by Candidatus Phytoplasma fraxini, a specific member of the aster yellows phytoplasma group that only infects lilac and ash trees. Over 20 species of Syringa are susceptible to lilac witches' broom. Common lilac (S. vulgaris) is tolerant and often shows no symptoms other than slower growth and shorter twigs. Japanese tree lilac (S. reticulata) and many hybrid lilacs are very susceptible to lilac witches' broom. These lilacs have yellow, distorted small leaves that often scorch brown on the edges by midsummer. Many tiny thin shoots form in clumps at the base of the plant. The shrub declines and is often killed a few years after the first witches brooms appear.”

You can take a sample into our diagnostic clinic in order to get a definitive diagnosis:
http://pdc.umn.edu/

Thank you.  Yes, I saw that description.  But, judging by my pics, do you think this is what my tree has?  And, anything we can do?

I think that you should bring a sample into the diagnostic clinic.  It's really hard to see the appropriate details in a photo.

You should prune out the affected branches.
There is no chemical cure for this disease.  Remove severely infected plants.

Although your tree may be a goner, perhaps it is worth adding relative to your lack of bloom problem that the major reasons are: 1) lack of sun, 2) soil pH too low (not likely in midwest), and 3) older trunks should be rotated out since newer wood blooms better.
good luck from a gardener in MD