If the dark area on the lower unit is where you think the weld is, that would jive with other motors I've seen.
other place to look for a crack down there is the rear bearing cone.
The holes in the tabs sticking out of the exhaust manifolds are indeed for hooking up ropes/cables for remote steering.
I'm now convinced that somebody (possibly even a dealer) swapped a model 156 magneto and flywheel on there in exchange for the original Owen-Dyneto unit. This was usually only done if the electric-start unit failed or burned out. 1930 was the first year that production outboard motors were offered with electric start. Other notable E/S motors of 1930 were the Evinrude Speeditwins model 167, Elto Quad, Johnson SE-50, VE-50, Caille model 47 (might have been more Cailles but I disremember the models) model 163 Lockwood Chief, and ummm ummmm ummmm I think thats all there was in 1930. In succeeding model years, some motors fell off the list (Caille, Lockwood) but Evinrude and Elto carried on using different versions of the Owen-Dyneto units until at least the late 1930's. I have a 1931 Elto Super C electric (model 607) that is as sweet a running motor as I could hope for.https://www.youtube.com/watch?v=1fOkvwh3Cxg
Your tiller handle is correct for an electric-start Senior Speedster. It has the slot cut out of one side for the speed control. With the Owen-Dyneto unit, the lever controls the timing advance. Without the electric-start, it can't do a whole lot. IF - and I say "if" because I don't want to look pushy - but "if" you want to trade that tiller for a conventional Sr Speedster tiller handle, I have one I would trade you. Otherwise, I'll cut a healthy standard Sr Speedster tiller to make it into the one I want.
Hope this helps.