A '30s Constantinople K. 18" at 1932 grams could make for a pretty decent little jazz ride. The cracks are, indeed, a serious problem.
You'll likely find no orchestral or marching players interested in it, except maybe for sentimental value.
The torque at the holes is tremendous when used as a hand pair, and those cracks wouldn't hold out long at all.
I'd drill a small hole at the end of each crack (1/8" bit at slow speed with cutting oil) - and use a decent magnifying glass to make sure you are at the end of the crack.
Then I'd put a grommet in the hole -- it'll help take some of the stress off the cracks. Then you could post it for auction as an 18" 1930s K. Zildjian Constantinople 1932g. ride. you'd likely pull in a hundred clams or so...
:2Cents: