Today the ticket price is around 95 DCR, but you can check it at https://dcrstats.com/
In case you don't know yet, there is a ticket splitting in test right now that will allow you to buy part of a ticket with much less DCRs.
No, that's just approximate ROI per ticket. Average voting time for a ticket is ~28 days, if I remember correctly (though, it's possible it could take up to a few months).
Fractional ticket purchases is being worked on now (so you can e.g. buy 1/2 a ticket and earn 1/2 the reward).
It's not yet ready, but in the roadmap: https://blog.decred.org/2018/02/28/2018-Decred-Roadmap/