There might be restrictions for GPS approaches, but I would think that
flying non-GPS approaches with the 430 should be fine since you're not
really using the database.

What about using it for locating missed approach holding points (a-la
NDB or DME substitution)? Since the database is out of date, you
can't use it for approaches, even non-GPS.

It depends on the HP - often it's a return to the OM using a
backcourse, or a nearby VOR, or intersection of 2 VOR radials. None
of these requires the database. Even an NDB would work if you have
ADF on board.