Your plan looks pretty good to me — a little rushed, but it will be fine since you have some extra days to work with.

I would not try to do “as many overnight trains as possible”  as you often do not get a good nights’ sleep and it’s disorienting and tiring to arrive in a strange city at morning rush hour.  Sometimrs, all you really want is a shower and a nap and you can’t check into your hostel (or sometimes even dump your backback) until mid afternoon.  I usually limit to an average of one, maximum two, overnight trains a week.  For 17 days,  I’d do 3 — 4 would be the absolute max. 

old lady,
 
If you had to change, add/delete on of the stops, what would you do?  Looking for suggestions.  Don’t want to be over rushed, but still want to see as much as possible.  thanks 4 the feedback