Hello all, after much trial I found a solution which seems to resolve so far. Below is the excerpt of virtual site definition that works. The key point was to convert the relative address with the line

ProxyPassReverse https://$HOST:450/ /  << $HOST address of my host

For clarity the << mark comments and are not part of the file.

<VirtualHost _default_:$PORT> << $PORT the external (https) port where Odoo will be visible   
ServerAdmin webmaster@localhost
 <Proxy *>
 Order deny,allow
 Allow from all
 AuthType Basic
 </Proxy>
 ProxyRequests Off
 ProxyPreserveHost On
 ProxyPass / http://localhost:8069/ << 8069 internal Odoo port
 ProxyPassReverse / http://localhost:8069/	
 ProxyPassReverse https://$HOST:$PORT/ /  << $HOST address of my host
 ErrorLog ${APACHE_LOG_DIR}/odoo_error.log
 CustomLog ${APACHE_LOG_DIR}/odoo_access.log combined
 #LogLevel alert rewrite:trace6 proxy:trace6
 SSLEngine on << etc. with the rest of secure site configuration 
</VirtualHost>

Enjoy Odoo behind proxy! hj