Is it too much water for one drywell to drain water from water softener & washing machine into it. Usual loads of laundry a week approx. 5 or 6

If you're using a dry well to drain your washer I'd install a grease trap,(see image) to trap the lint before it clogs up your dry well.

too much water for one drywell to drain water from water softener & washing machine into it Not if you don't discharge both at the same time, Good luck, Tom