The weight will be fine, I can’t believe that spindle weighs so much. We started this whole thing with the flex shaft foredom and it does work well but it is expensive and lacking power.
Your frame is large to want to do aluminum and pcb’s both of those I would recommend as small a frame as possible. Wood and plastic, no problem, but metal and pcbs are two ends of a different spectrum. For pcb’s I’d say the foredom would be best, Aluminum the spindle for sure. It is a multi machine but you are definitely going to the extremes on all levels, large build volume, heavy tool, hard material, and super precise pcb’s. Not saying it can’t be done, just take you time to set up your paths and get your feeds and speeds correct, Let us know how it goes.