Pass - 3D - 3S - 5D
?
I prefer a double here to be takeout, length in the two unbid suits
and some spade tolerance. With the actual hand I would pass and
hope for a plus score, maybe glad that we're not in 4S since I have
only a singleton spade. The "theory" is that when the opponents
preempt the bidding it is more useful to say "I have a little something
and maybe we can make something at the five level" - rather than to
increase a +50 score to +100.
I'm not sure about the second part of the question:
Pass - 1D - 1S (?) - 5D
?
While I still prefer a double to be for takeout if partner could only
overcall at the one level maybe you could make a case for double to
be penalty. To be consistent and unless I'd discussed it with pard I'd
stick with takeout. If pard has no defence and declarer ends up with
only one diamond loser why do I think we can defeat 5D with my actual
hand, as provided?
Hope that helps,
Oliver