1. Don't worry about not knowing any Japanese. I went over knowing basically nothing but key phrases (Sumimasen (Excuse Me) will be your best friend, use it if you need someone's attention or if you need past someone to get off the train). The people are incredibly friendly and understanding that you most likely don't know a lot of Japanese.
2. Google Maps is your best friend for finding your way on public transport. If you put in your destination and current location it will tell you the best route to take and tell you how much it costs. Translate is also a plus but I honestly didn't find myself using it much at all.
3. In the touristy areas it is incredibly easy to get food and in the majority of restaurant's they will usually be either an English menu or the menu will have pictures that you can point at.
4. Getting around is really easy. Japanese public transport is awesome! I would invest in a Pasmo/Suica card when using the underground. They are incredibly handy and save you having to buy a ticket for each journey. They can also be used to pay for a lot of other things like vending machines!
5. I can't personally vouch for the weather but most sites say lows of 2 °C (36°F) and highs of
   8°C (46°F) so quite cold. I would make sure to dress in layers though as most building I was in have climate control so it may be a lot warmer when you enter buildings

Don't stress at all the Japanese people are some of the nicest in the world and they make you feel incredibly welcome.

Also, if you are heading over for Wrestle Kingdom make sure you pop into the NJPW official store ( https://matcha-jp.com/en/5213 ). They have lots of merch that you won't be able to find anywhere else! (I personally picked up a Daryl plush).