I can see two kind of errors in your log files.
SEVERE: The web application [/liferay] appears to have started a thread named [org.python.google.common.base.internal.Finalizer] but has failed to stop it. This is very likely to create a memory leak.
This issue is related to Tomcat, and it means that it wasn't able to close properly.
Then you have this other issue
SEVERE: Failed to initialize end point associated with ProtocolHandler ["ajp-apr-8009"]
java.lang.Exception: Socket bind failed:  Only one usage of each socket address (protocol/network address/port) is normally permitted.
It looks like there is another Tomcat process started in the system (or another process binding 8009 port) and it is not able to be started. Maybe it is related to the above error. Could you open the task manager to check if all the processes were properly stopped?
Appart from that, I don't see any error related to not been able to add post in message board.
About from that, for security reasons, the Liferay folders and files have root:root or tomcat:tomcat permissions. If you want to modify a file using WinSCP, you have to modify its permissions first, using chown to change its owner.
For instance, if you want to modify the content of the /opt/bitnami/apps/liferay/data/portal-setup-wizard.properties, which has tomcat:tomcat permissions, you have to execute
sudo chown bitnami /opt/bitnami/apps/liferay/data/portal-setup-wizard.properties
In case you want to modify all the files inside a folder, you can use the -R option. The following example would change the permissions to the files inside the conf folder
sudo chown -R bitnami /opt/bitnami/apps/liferay/conf
Then, you will be able to modify them using WinSCP