I'm not sure if you're in the UK, or which country you live in Hideki but I'd recommend checking out the resources on European Casino Association (Click Here). There's a list of Self Exclusion Portals and Helplines for many countries within Europe. If you are in the UK I'd recommend GAMSTOP. I know you have said a lot of your accounts are on timeouts but you have mentioned that you often will then make another account. It will remove the risk entirely if you can take advantage of a self-exclusion option within your country, which lifts a weight off your shoulders. Check with your bank too - I know a lot of banks within the UK will block gambling transactions at a customer's request, so this may be an option for you also.
With regards to watching Will, or playing on demo-mode, if you feel these help you to satisfy the urge to gamble, then that's your choice. I would say if you've referred to gambling as an addiction for yourself then you should look into exclusion options before continuing to play on demo or exploring other avenues of gambling-related content. We love having you in the chat, and you have said you enjoy playing on demo, but you need be sure that doesn't make you feel you might win, and doesn't encourage you to continue to play with real money, especially given that you've said watching Will can make you feel jealous. A lot of people that have struggled do still watch gambling content and enjoy it, but most of those people are excluded and can't sign up even if they wanted to. Just be careful - demo-play can certainly be fun for some people, but my honest advice is to make a clean break from participating in any play if you are struggling, even if it isn't real money.
I think it's good that you're trying to set boundaries through cool-off & time out options, but I am quite firm in my opinion of those. I think they are fantastic options as preventative measures to ensure you stay in control, but I am clear in that I feel as soon as you need to time your account out to stop yourself from gambling, you've probably lost control, in spite of the fact that you have said you do have control. At this point my recommendation would be to time your account out for the maximum amount of time the respective casino allows, reassess your relationship with gambling, and look into self exclusion. To be clear, I think these options are brilliant for all players to ensure they have a healthy relationship with gambling, but as soon as you feel you cannot stop yourself from gambling unless you time your account out, I feel very firmly that you should not be gambling.
If you need any help please reach out to someone on the forum, and please consider what I've said. You have the rest of your life to do anything you want. Joining an exclusion scheme won't hinder you in any way. There's no benefit to spending any amount of time being miserable, and there is no shame in having a gambling disorder.