Winter Trip Tokyo-Shirakawago-Kyoto-Osaka

Hi, I will go to Japan in January for 7d 6n.
I'll arrive at Haneda early morning and depart from Kansai at almost midnight.

My rough itinerarty will be:
Day1-3 : Disney (either Land or Sea or both), around Tokyo
Day 4 : Tokyo - Shirakawago - Kyoto
Day 5 : Kyoto
Day 6-7 : Universal, around Osaka

Is the schedule doable? Any recommendation? Is it possible to squeeze an onsen trip in between my schedule?
The only thing I'm worried about is the luggage (I couldn't possibly bring my luggage along to Shirakawago! Do you have any idea (maybe put them in locker?), because round trip Tokyo-Shirakawago-Tokyo would be to wasteful (or not?)

And which pass should I buy? I heard there are many options, ones I know of are :
1. JR Pass + round trip bus from Kanazawa to Shirakawago + local ticket to go around Tokyo, Kyoto, Osaka
2. The new Hokuriku Arch Pass + round trip bus from Kanazawa to Shirakawago + local ticket to go around Tokyo, Kyoto, Osaka
Which one is more affordable and convenience?
3. Buy 1 way ticket for each destination

During January what clothes are appropriate to battle the cold? (I come from tropical country and this is my first winter trip)

Thank you!

It depends on how you are getting to Shirakawa-go. From Kanazawa or Nagoya. Either would have lockers for luggage. If not you can Ta kyu bin (postal service found nearly anywhere) to your next hotel.

Day 4 : Tokyo - Shirakawago - Kyoto
This looks hectic

Day 5 : Kyoto
This looks short

You are trying to see 3 different regions of Japan, Kansai + Kanto + Chubu
Usually people spend a week in each place but you are instead spending three days or less at each. I wouldnt try to cover all that, but you seem interested in seeing/visiting specific places of the country instead of soaking in each region's charms... To each her own, I guess.

Well, if you are from a tropical country that means you will probably feel very cold. It depends on the person as I know people who need the air con at full blast every time. For myself, walking in Vegas' summer under the sun for 30 minutes is bearable...

My reccomendation is simple, for a feel of what Shirakawa-go would be like go to the freezer department in a supermarket and stand there without moving for 10 minutes. (Shirakawa-go would be colder but as you would be moving about got to add a feel degrees up) Then put on a jacket and then the next one till you feel comfortable. Gloves are a must.

As for Osaka, Kyoto, and Tokyo these would seldom go below 0 (go stand in the chiller section of the supermarket). Though freak weather is commonplace anywhere in the world these days...