1 across: Small fortune with strings attached? (4, 5)
I wouldn’t flinch at anyone claiming $5 “is a fortune” to pay for a potato cake, but that doesn’t mean that fortune should mean grand in a cryptic crossword.
9 across: Mark in Vietnam — or Romania — rejected drug action (5)
This could have been Gold if not for the incorrect action = verb. Instead, it’s clearly Bullshit.
20 down: Pulse climbed with old exercise regime (3, 2)
If I remember correctly, I’ve heard DA himself complain about the tendency British cruciverbalists have of using initials for words that do not ordinarily go by their initials (for instance, having cold = c is fine, but trampoline = t is pulling the other one).
But regardless of whether or not it was DA who expressed that opinion, one with which I wholeheartedly agree, old = o is just not on.