NO. Doing that without the connection guarantee is not something I would do. It would be very unwise if you have a same day connection.
Late on Amtrak long distance services can mean VERY late, and 4 hours is not a great amount of time, especially when connecting from a western transcon at Chicago. On the ASMAD site (
https://juckins.net/amtrak_status/archive/html/home.php ) you can research how often a connection is made, it shows that since March 1, that connection has been missed
34 out of 111 times, or 31%.
Personally, more times than not, I build an overnight layover when connecting at Chicago eastbound, so as not miss sleeper accommodations the next day. If you do build in an overnight layover in Chicago, then yes, breaking the reservation at Chicago is safe. If you are making a same day connection, under no circumstances do it under two different reservations.
If you miss your train with both under the same reservation to Harpers Ferry (served only by the Capitol Limited...if you were going to DC, they might do things differently, like put you on the Lakeshore Limited later that night), Amtrak will:
1. Provide you with a hotel at their cost, billed to their account.
2. Provide cash for taxi transfer and meal costs
3. Provide transportation on the next day's Capitol. If you had sleeping accommodations, you might be put in coach if the sleepers are full. Amtrak will refund the sleeping car accommodation charge in that case.
If you miss your train with them under separate reservations, Amtrak will:
1. Show you as a no show, no refund of your fare.
2. Demand a new ticket be purchased at current prices on the next day's Capitol Limited.
3. Leave you to your own devices to stay the night in Chicago.
If you are breaking the trip into multiple reservations, do it at a point where you do NOT have a same day connection.