Although I normally work the diner, I do occasionally work the sleepers.
I EXPECT a sleeper attendant to do all those things you list and do so WITHOUT need for a gratuity.
A gratuity I might extend is for extra service, such as: getting a special dinner reservation request fulfilled, checking by periodically, bring water or coffee by without having to be asked, being visible (not hangin' in the diner), being knowledgeable about our route, making sure ALL previous guest trash and leftovers are gone from my room before I enter, or maybe wiping off the window.
A gratuity is not mandatory, and in my opinion, will not be extended for service that defines the do-no-more-than-required attitude.
As far as getting dinner reservations filled, that's up to the dining car lead, not the attendant. You should request the attendant to check periodically, many people find it annoying to have someone come by their room every hour since most people ride in the sleepers for privacy. Again, you should request water or coffee, we are not psychics, we won't know when you're thirsty.
As far as wiping windows, we do not have the supplies for that. We are not allowed to use any chemicals or supplies outside of what Amtrak issues.
I am relatively new but listening to the "old timers", I often hear about the old glory days when first class passengers were "first class passengers". No one was running around without shoes or a shirt, throwing trash every where, or receiving service without tipping.
Gratuity is not mandatory, however it should be given as long as good service was provided. We shouldn't have to do cartwheels, back flips, and handstands for a $5 tip. Your attendant helps you on board, makes your dining reservations, puts down your bed, offers wake up call, helps you with your luggage, waters the car to make sure you have a working toilet/running water, is at your call for the duration of the trip, makes up your bed and clean your room when you detrain. I'm sorry daveyb99 if you feel more should be done for a small tip.
What I notice is those who ride without running you all over the train every five minutes are those who tip the most. I don't mind providing this service, it is my job, however I do mind those passengers who treat you like their personal slave. I had one lady who called me to turn off her light (and on when needed), not because she didn't know how, but because she felt that's my job. The tip left - $3. I had one man who requested all meals brought to his room and an extra sheet and blanket because he liked to sleep sitting up. That meant I didn't need to bring down and make any beds in that room. I came by his room but he requested to have some privacy and if he needed me he would call. He left no trash in the room, not a speck and when I helped him off he gave me $100.
The expected tip for expected service is $10 roomette, $15 bedroom (these are a pain to make up/clean up). Anything above and beyond is at your discretion. I love the idea of handwritten thank you notes! We work very hard to make your trip comfortable and pleasant and it feels good to know that it is appreciated. A thank you note or a complimentary letter to Amtrak is worth more than the monetary tip.