It looks to me as if it is the rust that is holding it together, so removing the Allen cap screw probably would result in it falling apart, as you say. In the old days it might have been repaired by cleaning out the radial cracks with a saw blade and welding them up before dismantling it, then welding it up more elaborately and dressing the welds where necessary. A new part is a tidier and more controlled solution, if the part is available. Personally I'd try to weld it, just because I'm an old guy and accustomed to working on old stuff for which new parts are either unavailable or too expensive. However I've made a lot of work for myself at times by following that approach.
