LOAD BALANCING BUT NOT TO GATEWAY

I have a loop network made of mikrotiks and ubi’s.

It forms a baseball diamond, with home plate being my incoming core connection to the internet.

First and third bases are two different ways to get to second base.

Second base thus has two incoming ports plus a third outgoing port to various customers.

Each base has their own mikrotik and ubis.

The link from home to to third base is overloaded, the link from home to first base is not.

There are many different subnets being sent via first or third from home to second base and then to end customers.

From home base I can hand route different subnets to third or first, and ospf will get them to second base and to the customer.

Presently returning packets all come back from second through first to home, but that upstream return traffic is minimal.

What are my options for putting routing rules or ospf rules on the home router to hand packets out to
third and first bases automatically, either by packet or by connection, across all the different subnets trying to get
to second base?

RTFM is welcome.

I am not that good as OSPF, it kind of mysterizes me. But it would be also useful if the home to third base link died, that
the home to first base would take over the traffic automatically and visa versa, including return traffic.

I am running ospf on all routers.

Thanks in advance.

Homer W. Smith
CEO Lightlink Internet