For a variety of reasons, I too think going with the 35mm focal length makes a lot of sense.
I would also encourage you to think about what others have said in this post about the attributes of the modern Canon lenses--outstanding IQ, IS in one instance, autofocus, and the ability to shoot manual if you wish to do so.
And think about how you may use this lens a year from now or five years from now. You might very well want that autofocus. I grew up with manual lenses back in the 70s. And I believe that you are correct in that slowing down will make you a better photographer. But at some point after you develop those skills, you may want to be able to take the quick fast shot. Also, you also say you enjoy street photography. In my mind, that means people, and people often move very quickly. In those situations, and in lower light levels, autofocus and IS can come in very very handy. So I'm not sure why you would give up autofocus capability when you can have it, and shoot manual when you want it, and have excellent IQ, all for a lower price. I would humbly ask you to consider that question before you make a purchase and also what you could do with the extra funds you may have as a result.