Japan/Tokyo Halloween

I'm planning a 1 month trip (to include the air travel time, typically 1.5 days one way/ 3 round trip) in November from Houston,TX. However, I can leave whenever I'd like. So my questions are:

1. Should I leave a bit early around Oct. 28 to fly into Tokyo to see Halloween festivities?

2. Not being super into Halloween myself, but are there enough Halloween festivities to see in Tokyo, other than the Halloween train party, to justify coming early?

3. I'm packing everything I will need in a 35liter backpack. So I won't have anything to dress up in for Halloween if I decide to come then. Are there any recommendations for shops close by I can go to grab a costume or make something by the 31st?

Thanks for any replies. I'll be on here much more once I get the ticket purchased, pending answers on this thread, to determine the itinerary.