Hi Virginia,
Let's walk through each problem one at a time.
1. In your DNS, please remove @ A record for 66.96.160.155.
This will leave you with one @ A record pointing to 52.162.107.11. Since your current TTL is 1 hour, you will likely still see issues for an hour or more after you make the change.
2. Use the plugin to change your wordpress site to the .com url. This should work properly once change in #1 above takes full effect.
3. In regards to DNS error, please give me more information about error and I will assist you. Please complete #1 and #2 above first.
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP