Ok, because there is only one remote site, MultiSite is not strictly required. It would be required if there were at least three sites in total.
Looking at the MultiSite config, the following policies are most likely needed:

At the other site add the equivalent policies for the other subnets.
My recommendation would be to:
1) Enable the default bypass policy rule #99 to start with
2) Find out what is causing the lan0 errors on the one site.
3) Make sure wan0 and lan0 are cabled the right way around.
4) Start adding the rules e.g. #91 and check that the peers come online.