I can relate to almost everything you are experiencing.
I am living in the north of Japan (Niigata) and have been living here for 9 years.
Living here as a Vegan is crazy right!
People think you are suffering form some sort of illness or are doing it for religious reasons. When I ask them why they think it's ok to eat meat, they say they know it's wrong but they can't stop because it's "おいしい" |:/
I'm lucky that my wife is Vegetarian and supports me (Even through my crazy 801010 raw food phase)
Trying to show the world here that Vegan is healthy is hard if you are not ripped, right?
Just know that you are not alone here bro!
Your dizziness maybe because you are under carbed but as you can no doubt see, just buying some peanut butter (natural) quinoa, lentils or oats etc... is IMPOSSIBLE here!
So it is hard to carb up if everything here is crazy expensive, heavily processed or covered in some type or oil, or just non existent!
There is hope however and it is the website http://www.iherb.com
You can order most things form there that I mentioned above, (Even gluten free rolled oats) but for quinoa, chia seed you HAVE to use ebay.( only way to get about stupid archaic customs) If you are interested pm me and I can give you the ebay user id's I buy from.
I am lucky enough to be friends with a farmer that grows brown rice (as close to organic as you are going to get over here) no animal fertilizer and is featured on SMAPs (boy band) tv culinary show.http://www.gensenmai.net
if you need to have it sent to you or need to know anything than I can help you with that!
The b12 thing is also a concern of mine. I am thinking of ordering some nutritional yeast from herb as it is loaded with protein and b12.http://www.iherb.com/Frontier-Natural-P ... 30832?at=0
Also here is a page for ordering Kale in japan. They use no chemical spraying either. http://www.masudaseed.com/
Doctors here won't understand or respect your choices for being vegan and that goes for Tokyo and will make you feel guilty for not consuming animal products, so...yeah scratch that one.
As for vitamin D...lets put it this way, I want to move with my wife and kids to Okinawa
All the best and if you need any help with anything please don't hesitate to PM me anytime!