A couple thing worth mentioning is that even with all that cleaning you have done you really need to desolder and remove any SMT chips that have been exposed to corrosion. the pcb below those chips likely has 'battery goo/acid still there'. probably good practice to straight out replace UD8 and any other badly corroded chips as they will eventually fail (due to the extensive corrosion on the pins its only a matter of time)
more could be said but honestly id just get a reloaded board myself and move parts over these days as long term reliability will be much better