Your son also appears to have lost the Bronze Tier bonus of 624 Avios (if I've understood correctly).

I think this is a mistake too, and it's either the Alaska connection or the DFW break that causes the problem I imagine.

You can either keep ringing or fill in the webform for "partner" flights (bottom of the transaction list). The trouble with that webform is I suspect that it will get rejected because it has given you some (but not all) your Avios. So you may prefer to go straight to the general customer service webform which gives you a text field to work with. You will probably need some patience. Please let us know how it works out.

There's a well known bug in the online TP calculator, so that get's no-one anywhere.