1. Not displaying feelings when in hardship makes people think that stoic people are grim, introvert people or something which is not true and that's why I don't like that particular definition. But yeah I would say that def 1 is relevant to stoicism.
2. I definitely think that applying stoic philosophy to your life would be much more enriching as it serves as very effective guidelines as how to handle life. I know I have benefited a lot from doing that.
3. The disadvantages could maybe be that you get neurotically consumed by it. Always be critical and do what feels right for you.
4. Sleeping on the floor would be a stoic way of pushing your comfort zone, so yeah go ahead and do that. Generally, always seeking to push your comfort zone in different aspects of your life would be a way of applying stoic philosophy. Also a psychological trick they used was negative visualization, which means to visualize yourself in a scenario, in excruciatingly detail, where you lost something you took for granted. Your own life for example, so imagine yourself dying in all kinds of different ways but also loosing persons you love and materialistic things you think you depend on. Negative visualization has number of positive rewards such as when things do get shitty and you loose someone or something, you will be more prepared for and it will be much easier to process the loss. It also makes you want the things you already have and you will learn how to appreciate it and not taking it for granted.
5. There will definitely be quite some suffering involved but only for a time, and compared to the suffering you're spared from by not applying stoicism in your life I think its a real bargain.
If you haven't already, read "a guide to the good life (the ancient art of stoic joy)" by William B. Irvine. Like a stoic self help book, (I think it's on Leos book list even) and I think it would answer all your questions .
Peace
