Offsetting fouls when there is a change of possession

[crimsonace1]

This happened in a sectional game a few years ago, but was one of the wildest things I've seen (and the officials talked for a few minutes to make sure they had it right. 

Team A throws an interception at the 50. Team B returns it to the +25, but a post-possession flag for holding is thrown on Team B at about the +35. At the end of the play, Team A is called for a personal foul (I believe it was a facemask, but might have been a late hit - and I understand one is a live-ball and one a dead-ball foul).

IIRC, the ball was taken back to the spot of the interception and the penalties enforced there and Team B retained the ball. 

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Alternatively, let's take a similar play but change the timing of the fouls. 

*-Team A throws an interception, but a flag is thrown for holding before the pass is thrown. Team B intercepts and is called for a post-possession holding penalty. Does A get the option to decline the penalty and keep the ball or is it an offsetting penalty and replay the down? 

[Bobref]

Whether the Team A foul was live ball or dead ball matters a lot. If we assume it was a live ball foul, like a facemask on the tackle, the Referee goes to the team last in possession — here it’s Team B - and gives them the choice of accepting or declining the facemask penalty. If they accept the facemask penalty, the fouls offset and the down is replayed. If, as is more likely, they decline the facemask penalty, they now get to keep the ball. The Referee then goes to Team A and, of course, they accept the penalty for the Team B holding penalty. That 10 yd. penalty is enforced in this case from the spot of the foul. 1st & 10 for B from the +45.

If, on the other hand, the Team A penalty was a dead ball foul, then both penalties are enforced, with the result being 1st & 10 for B from the +30.

In the alternative scenario, since Team B got the ball “with clean hands,” i.e., they did not foul prior to the interception, they can keep the ball by declining the penalty for A’s holding foul. Then A will accept the penalty for B’s holding foul on the return, which will be enforced from the basic spot which, depending on the yard lines involved, could be either the end of the return, or the spot of the foul.