I haven’t owned this laptop. But I can’t imagine it to be totally different from other models. For the components my guess is as following. I can’t imagine it to be a lot different than that.
The battery has 45w/h and 2 cells (7.4V). Taking into account fast charging with 1C (45w) and max load of 35w (which will drop anyway to ~25 after a short time period) a 80w power supply should do the job perfectly. I believe even a 60w power supply should not hinder in any way.
My guess is that the internal voltage regulator works with 12+V. So anything from 14-20V should be fine. Amperes would be 3A (20V) 4.3A (14V).
With ThinkPads I have experienced that the voltage Input is quite flexible (nominal 20V, but works with 15-23V)