The losing of texture and showing of boxes is to make the orbiting keep up. When you stop dragging they will come back.
What is most likely being demanding enough for the textures to be hidden is your vegetation. If you could find a simpler version of those models everything will improve.
You also have been opening the backup file and not your working file. If you get a crash and open the file with a ~ in the name, and crash again, and then open the backup file, it then has two ~ in the name. Each time you’re doing that you are opening the copy of the previous saved file. The file without the ~ is going to be more recent.
Also, in the welcome screen there will be some thumbnails of a Recovered file. That one is more recent than your last saved file, you might try using that to lose the least amount of work.
In a case where you have good reason to open the backup file, like for example if you hate all of the recent changes you made, and want to go back to your previous version, then use the ~ version, but rename it to something without ~ in the name. Or open it and then save as to a new name.