Multixact wraparound monitoring

Hello.

I just had an outage on postgres 14 due to multixact members limit exceeded.

So the documentation says "There is a separate storage area which holds the
list of members in each multixact, which also uses a 32-bit counter and
which must also be managed."

Questions:
having a 32-bit counter on this separated storage means that there is a
global limit of multixact IDs for a database OID?

Is there a way to monitor this storage limit or counter using any pg_stat
table/view?

are foreign keys a big source of multixact IDs so not recommended on tables
with a lot of data and a lot of churn?

Thanks

-- 
Bruno da Silva