Toller your issue is simple , the other ideas are misguided. You have a NE exposure in shade and mold is growing , its normal and unavoidable to an extent but can be controled. In your past cleanings the mold was not killed off the bare wood and is ruining your finish, mold eats paints. If its in fact peeling and not also boards holding water from the crown of the wood facing up. If boards were instaled crowned down so boards don`t hold water then mold is the only issue. Get a garden sprayer and cheap laundry bleach, use full strength, spray it now and it will look better. If you want to restain, powerwash, then kill the mold off the bare wood by spraying and powerwash it again. You don`t get rid of mold by just power washing, its spores remain in the wood alive to ruin your finish again. After wood is dry restain with the same product if you wish. Add a mold killing additive-although one is in your product already and should be enough. 2 things here, once your deck looks dirty in the months ahead, its actualy mold again, so spray on some bleach to keep mold from growing again and ruining your finish. Second, Solid Color stains do peel, Semi Transparent are better for decks but require more maintenance. But stripping it is not worth it now.
If you kill the mold off the bare wood with Bleach full strength and keep it bleached whenever its dirty [actualy mold] it will last longer. dirt washes off, mold doesn`t, but at first looks like dirt.
You need warm days and nights to stain properly, as the directions state. I live in shade with alot of wood and use a garden sprayer to apply 2-8 gallons bleach every year for Mold Control, it always comes back. A garden sprayer and laundry bleach will be your best friend. You might need to use it every month or so in certain areas.