Kyushu trip on December 2016

This is my first time travel to Kyushu, have some questions to ask here:
1) SL Hitoyoshi Steam Train not service in Dec 2016? I found the timetable stated until end of Nov 2016 only. Really hope can take this unique train.
2)Aso area is open for traveler visit during Dec 2016? Understand that April earthquake destroyed the railways in between Kumamoto and Aso.
3)Planning to go Oita from Kagoshima for 2 nights stay, wanna take Hayato no Koze and Shinpei to Kumamoto, and takes other train to Oita. I have to spending the whole day in different trains and reach Oita in the night. Any better suggestion?
4)From Oita to Takachiho, this need 1 day trip or half day trip?
5)Oita, Beppu, Yufuin, which place is recommended to overnight?
Thank you in advance for the advice.
This is my first solo trip, wish to have a smooth trip~

1) It looks like you've already seen the official info on
http://www.jrkyushu.co.jp/english/train/sl.jsp
so you already have your answer.

2) You can still go there. See:
http://www.japan-guide.com/news/0035.html
However, you currently can't get anywhere near the volcanic crater. Latest info is at:
http://www.aso.ne.jp/~volcano/eng/index.html
http://bit.ly/2gNOpoL
And if interested, you can see what you'd be missing at:
https://www.youtube.com/watch?v=Tyh_nKrv5tY

3) Not sure what you're asking. You want to take the old school train but you're not happy about the time it takes? You could get from Kagoshima to Beppu in as little as 3 hours 15 minutes or so. But that is taking the bullet train a lot of the way. A Kyushu Rail Pass can also save you some money.

4) Given that you have to take a bus or drive to Takachiho and the time it takes, I wouldn't call a half day trip worthwhile.

5) Depends on what you want. Yufuin could be either a lot more relaxing, or a lot more boring. Beppu has more than just its hot springs - the Hells Tour doesn't take too long and while a bit kitschy in some places, it is well worth it. The nearby Takasakiyama Monkey Park/Aquarium is one of the better ones in the country as well.
https://www.youtube.com/playlist?list=PL7LcPcmoSg-hOggZamc2lUNTr46ApKX...

If you are really looking for a great hot spring experience, consider Kurokawa in Kumamoto. You'd need to rework your itinerary, but it can be quite a treat.
http://www.japan-guide.com/e/e4575.html

Thanks Ken for the advice.
I will rework my schedule :)

People go to takachiho for the yokagura, which to my mind isn't all that interesting. It is very traditional Japanese culture. If you aren't there for that, just the gorge and shrine than half a day is sufficient. The lodgings are over priced for a location with nothing much to see or do. Though I must admit the sunrise as we drove out was nice. The Rays spread over the countryside as we were descending the mountain.