RE: batttry question
Cos they don't want people to fast charge them and warranty them if a cell isn't very good and suffers, despite the fact that these kind of cells should take a 10A charge comfortably. It's like almost all 'manufacturer recommendations', overkill. Don't get me wrong, unless you have experience and are sure of what you are doing, you should always follow the recommendations, however, as you spend more and more time around this stuff, you learn what is actually true and what is just wasting your time. As the others have said, you will be absolutely fine charging it at 5A.
Good batteries have no such guidelines on them, people know what to charge them at.