Stainless steel is considered the best material to come into contact with bronze, if the contact is long-term, in order to avoid electrolytic corrosion of the bronze. These two materials have similar reactivity to electrolysis, unlike bronze and regular steel cable, for instance. If necessary, you can use a small piece of stainless steel such as a hook, and make the rest of the cable of any metal.
As for the point of suspension, I always have inserted a support or places to secure the bronze to a base before casting. It usually fits more or less within the actual sculpture and doesn’t increase the size or cost of the mold. You can use one or more pieces of wax, shaped into the correct form and with or without holes punched in the wax. Balance in the wax piece will be similar to that of the finished bronze, so long as the original piece is all wax, or totally of material having a like density. If you need a threaded hole, that should be done after casting, though an initial hole of slightly smaller size can be punched in the wax.