I will use opewnsource as long as I find it useful, I will switch to premium only when I am restricted by the open source. I have been using wordpress for many years and have no desire to switch to any premium software. However, after using SMF for 4 years, I switched to Xenforo
Well, I have never streamed but I have participated on a few live streams. The platform depends on your content. Twitch and Youtibe might be good for game content, Kick is basically for gambling related content.
I haven't backed any game developer on Kickstarter but I have backed a couple of innovative ideas. Getting financing is becoming very difficult these days, however, crowdfunding platform like Kickstarter makes every thing easy. I think crowd funding will grow bigger and bigger.
Do you want a full control over your databse and website files, try woocommerce, if you wnat a simple platform, or Magento, if you want a powerful solution. If you do not want to manage form back end and want an easy solution, use Shopify.
I always write on Word document, however, once I publish it on my website, I delete the saved file. I do not keep it saved on my device. I regularly create back up of my website.