You'll be fine booking for 2 and when you arrive at the restaurant let the CMs at the podium know you are a solo diner. As long as you show up for your reservation you will not be charged for the "missing" second person. You don't need to call in advance to modify the res since there are no tables for 1 and you'll automatically be seated at a 2 top. The only time I would call to modify a res would be for any pre-paid reservation (e.g. dinner shows, Wishes Dessert Party).
The Disney dining reservation system has a known glitch that makes it hard for odd numbered parties (1, 3, 5 etc) to book. The system wants to fill all the seats at a table so if you input 1 person it passes over tables for 2. However, if you input a party of 2 you will often find plenty of availability as you found for Akershus. Go ahead and book the table. As a party of 3 we often have better luck when searching for "4."