We won't work on Bosch products so this is more general info, but you may find it useful. The problems you describe happen to all of them anyway.
Door not opening happens to all of them now and then. If you're worried about grime/lime left in the washer holding the soap door shut or otherwise causing a problem, use this:
Use as directed. It's really good stuff.
About soaping, you really can't gauge how much soap to use without knowing how hard your water is. If you have 15 grains of hardness (most of the USA is around there, though it does vary considerably), a 'pod'/recommended powder amount is about right. Lower hardness means less soap (and don't use pods), more hardness means more soap (or 2 pods). The problem with detergent is the government required them to remove phosphates a number of years ago. Now they all basically suck...
White stuff in the bottom, you say? is it like a mineral-looking white or a soap looking white? Too much soap causes suds (you want NO suds at all even during a wash in which you added soap) and the drain pump can't drain suds. Then, when you start it up again, it will still have soap left over from the last wash. It's a compounding problem. We remove the soap and suds with a splash of Spa anti-foamer, but a little vegetable oil can work. That cuts the suds and allows the drain to fully drain out the water and soap. If the water is mineral-filled, that's a different issue, however.
over-soaping is more of an issue if you have a water softener like people where I live. The water is SO hard that we need softeners. A local softener place makes REALLY good softeners so the water comes out totally soft, as opposed to most which still leave some hardness. Add that to the fact that local stores sell LOTS of those pod things, and we have a recipe for everybody using way too much soap. It's so common that we will run through a checklist when people call with dishwasher problems to make sure we won't go out on a call just to tell someone they use too much soap.
If you leave the soap door open, some of the soap will get drained out with the pre-rinse water, but not all of it. It doesn't fully drain and refill. It is a viable option we tell customers if they have a broken dispenser that is no longer available and they don't want to buy a new dishwasher. It's not as efficient, but it's not terrible. Some of those pods/bricks are actually designed to be thrown in the bottom anyway. Powder isn't, but it can still work.
'Rinse Aid' is important, but only use the good stuff ie. name brand. Generic stuff often causes more problems.
Usually when you remove the cap to pour in the rinse aid, there will be an adjuster for amount. If you think it's too much, you can turn it down.
Films can be caused by the water not being hot enough. This will cause soap to not dissolve as well as it should/not remove crud as well. Dishwashers get their water from the hot side of the kitchen sink usually. Run the faucet HOT before turning the DW on. They don't fill up with water enough to 'run out' the cold, and the heaters inside are really not up to the task of heating cold water as hot as they need to. Some DW's will drain the water out and refill up to 5 times if they don't sense hot enough water. Some new ones will also try to heat up fully anyway. This can take MANY hours, but some will do it. It's really that important.
