You are free to make your own choices about your diet and lifestyle. However, this site as about facts not semantics. You chose to claim that these ingredients were "traditional" (spreading this myth) when it was neither accurate nor relevant to the question. Japanese sushi is almost exclusively seafood-based, although there are many dishes influenced by it that are not. Shojin Ryori is very rare and is a completely unrelated to sushi that happens to be from the same country, this is illogical (it is like claiming hamburgers are vegetarian because some Americans eat felafel).

Sushi means "rice seasoned with vinegar" (not onigiri or sashimi) and it is traditionally served with eggs, fish and seafood (Japanese language is highly contextual). In Japan, nigiri sushi is more common than maki rolls and avocado, carrot, or capsicum are not traditional ingredients (although common western countries) nor is it a traditional breakfast. These are good recommendations but this answer is factually inaccurate. Japanese cuisine often uses seafood or fish-based seasoning and is rarely vegan or vegetarian.

No. It is so rare (virtually unheard of) that overdose is not a concern for medical practitioners. Higher doses are routinely given when required for various reasons. The main concerns for OTC treatments is cost and purity.

You can, it’s just inadequate to rely on one long-term. Your body needs sources of many amino acids and it’s best to consume a combination of foods to ensure that you get enough to be healthy (if you have the luxury of the wealth to do so).

Bear in mind vegans (to whom this issue is especially pertinent) also use this site and their requirements may differ.

I think this addresses the question: everyone’s requirements will differ and this is best decided in consultation with a medical professional (with regular tests).

Indeed it appears that it is. My minor mistake, it does not affect my heath recommendations. Next time, you are welcome to submit an edit request to address such minor inaccuracies.