In between, I asked if I buy an extra ticket from Amman to Doha, can they check me in with the second leg of the original flight at the same time? no. This I kinda understand...
Normal airline procedure is if you no show a segment all subsequent segments will auto cancel.
As above in most places in the world/most airlines check-in and ticketing/re-ticketing (& bag fees) are very different functions. Check-in agents getting involved in tickets/money just slows every one on the queue behind. USA is different.