#1 Yes. You are likely to get a speed that is not what you finally intended. It also forces the old fragile gearing. I have read and follow the procedure of setting the speed, cocking, firing the shutter to make sure it is working at that speed, composing, focusing, cocking and firing.
#2 probably. The potential is to forget to reopen and fire the shutter. If you leave it too long (a month or two) the shutter will freeze and you will be paying $80-$120 for a cla (clean lube and adjust.) Painfully, I have done that with large format. It is a waste of time and money, but it makes the lens more valuable when you sell it if the cla is recent.
"If you want to be famous, you must do something more badly than anybody in the entire world." Miroslav Tichı
What John said. Also, occasionally take your cameras out and run them through their paces, even when not loaded. The oldies especially need to be exercised so they don't get arthritis of the shutter kind.
Age and exercise related jokes aside, welcome to APUG. You will find much help here.
If you are new to folders you may also enjoy and benefit from the Rangefinder forum at rangefinderforum.com. They have a category specific to your interest with multiple threads answering these and other questions that you may not yet have encountered. That category is called 120 folders. Take a look at some of the threads and answers. You will meet more enthusiasts with questions and answers.
One thing with those older shutters is that between age and use, spring stretch is a very real problem. When I was done using my folders, I would put the shutter down to B or something low for storage, uncocked. That way, there was the least amount of stress on the assembly.