No Stupid Questions

My weeb ass: My time has come.

I did it, and for the record my native language has absolutely nothing in common with Japanese. I started with Duolingo and kept at it until I could power through easy manga, at which point and I started doing that. The good news is that if you can power through the early bits, your entertainment (assuming it's in Japanese) will supplement and eventually replace your studying. Here are the things I think I did right:

1. Be willing to invest serious time into studying and/or consuming comprehensible material (also known as immersion). At what point it becomes "not worth it" is up to you, but I'd aim for at least an hour a day.

2. Watch anime often and attempt to understand what you're hearing (this is separate from studying). You'll fail most of the time at first, but this keeps your ear open so you improve your listening without doing much if any extra work. It also helps you keep track of your progress, since the better you get the more you'll understand. I took a half-year break and when I came back I found my Japanese had improved at least in part because I was watching anime in the interim.

3. Don't fall for the studying trap. At some point, and probably earlier than you expect, you'll have to drop actual studying material and focus your efforts on immersion. I started by reading a manga called Yotsubato after getting to conditionals on Duolingo, but really any manga with furigana works. If you find something other than manga you like better then go for that, but you need something and it needs to at least keep you on your toes language-wise and still be ultimately comprehensible. Humans learn language by recognizing patterns within copious volumes of content, not by rationally analyzing those patterns; that latter stuff is for linguists.

4. Keep challenging yourself. It's easy to think you're not ready to advance to the next level, but you should accept that the transition will be painful anyway and often try your hand at more advanced material (meaning immersion material here, as I said don't bother with advanced studying material). In my case, I thought my Japanese was plateauing after sticking with one thing for too long, but after I read my first light novel I improved ridiculously fast. We're talking serious improvement in a matter of weeks here. You're likely to underestimate the level of material you can digest, so you should take that into account when making decisions.

Note regarding your native language: I speak basic Chinese and Chinese and Japanese are different enough that you'll be almost no better than an English native speaker when it comes to fundamentally understanding the language. However, the writing system and the prevalence of Sino-Japanese words mean that you'll have a leg up in guessing the meaning of words you don't know when reading, especially after you learn to reverse engineer character simplifications. For example, you'll see something like 解説 and be like "oh that's just 解说." At least coming from the other direction this is super convenient, but it's obviously no substitute for actually learning the language ~~and it won't help you at all when it comes to listening~~ (this is the case for Mandarin, but apparently Sino-Japanese words are pronounced reasonably close to their Cantonese counterparts). You also get the joy of seeing exactly how the Japanese butchered Chinese words, so... uh... good luck. You'll have fun with 样/様. On the plus side you won't be like "what the hell is this" when you run into counters, but the counting system still has "fun" stuff for you. So to directly answer your questions:

YMMV, but I don't think it's hard at all. With the benefit of hindsight, it's no more or less difficult than English.

If you can commit then no, but obviously yes if you give up in three weeks.

This isn't as important a decision as you'd expect, but Duolingo will do fine.

PS: There's more and more anime with good dubs these days.