There is a blog article available describing ways to find symbols (from your installed collections):

When you hide ALL other layers, you also hide the symbol definition layer, which cause all symbols to be hidden, no matter what layer they are on.

For the door, it sounds like you just were the "victim" of smart symbols and snapping. Smart symbols are intended to align symbols correctly to lines (like walls) and are mostly helpful, but there are situations where you don't want/need it as well. It also sounds like you may have snap on, but not cursor snap which can lead to some confusion because the snap doesn't happen until you click, instead of continuously.

So, right click the snap button in the lower right, and make sure both snap AND cursor snap is disabled (You usually don't want snap for placing doors, but you may want to turn it back on for other things, and then it is best to have both options ON). You should now be seeing the door snapping into place as you move the cursor. Which way it is oriented should be determined by which side of the line your cursor is on when placing it, so try subtly moving the cursor right across the centerline of the wall to turn it around (just a very tiny movement required).

If you cannot get it to behave, you can also turn off smart symbols by right clicking inside the map with the symbol on your cursor and just turn off the option called "smart tracking" which is what causes it to track lines.

For the fill style issue with the drawing tools, it looks like you have picked the wrong drawing tool style for that map type. That should normally be loaded automatically, but based on the fill I see in the screenshots, I think it should be set to "Dungeon DD3 color" and not "Dungeon SS2B". Is it right that you started this map using the DD3 Dungeon template"?

You're not technically supposed to "choose a style" in that dialog. The style selector should be prepopulated with the correct style choice for your current map.

If you want to use drawing tools belonging to a different map type than the one you are working in, you need to import the appropriate fill styles first. More about this in this faq topic:

You can't. There is no way for one member to block others seeing what they post. Besides, this being a public forum, people can browse it and look at the images even without an account at all, so banning wouldn't really work even if you could.

For comments, if someone is sending abusive comments or engaging in undesired behavior, you should report them to a moderator. If it was done via private messages, you can add a moderator to that conversation so they can more easily see it themselves.