There are multiple factors you need to take into account when trying to grow a channel. The quantity of uploads is one but not the only one. Most pros will tell you to upload at least 100 videos in 1 year, so basically about 2 a week. This gives Youtube a chance to evaluate your channel and determine several factors they can use to determine how to share your content to more viewers. But you also need to take into account the quality of the content. YouTube won't share a video no one wants to watch. Targeting a specific audience, what we call your ideal audience, is the best way to make quality content that can get you more views and thus eventually get shared more.
Yeah, two or three times a week is good. However, you need to spend a lot of time studying video production to make your videos better. It will do no good to upload two or three times a week if your 100 video is just as bad as your first video.
It depends upon when your audience most likely want to watch YouTube, and how much
YouTube they can watch per week, and then tailor your content to those watching
habits. Generally, once or twice a week is enough for uploading videos to Youtube.
It depends on the appetite that your audience has for your videos. For many, it seems that once or twice per week is enough to sustain a channel. There is also the idea that more uploads means more chances of getting discovered. However, you do need to give videos some "breathing room". I seem to remember reading a recommendation of putting one or two days between uploads.