No pass but regular tickets on the IC (not Thalys which can cost much more, requires advance booking and is marginally faster) that go hourly from Antwerp to Amsterdam. You cannot use the ABS (All Belgian Station) fare to go from Brugge to Antwerp as i suspect the ABS destination must be from Brussels and not going in circles involving three stations

I would think any means any one station but not sure. If i needed an authoritative answer to this i would call BETS 800-441-2387 and ask - that's what i do when i need a definitive answer and always get one. IME even though you already have a ticket they will give you a definitive answer. Sorry i cannot get the link you provided to work so cannot read the language but i doubt if it permits multiple rides to multiple stations - i would be interested in what your definitive answer is.

this copied straight from Thaly's regarding the Any Belgium Station fare:

The "Any Belgian Station"("Toute gare belge" or TBG) fare enables you to extend your Thalys journey at minimal cost by changing to a train on the Belgian rail network, or to travel back to your Thalys departure station from any station in Belgium.

Travel on internal Belgian services is valid two days after the departure or arrival of the Thalys service. You may travel on internal Belgian rail network as from the day before your outward Thalys journey, or until the day after your return trip.

With the ABS fares, your international Thalys ticket is valid for 1 journey between any of the stations on the national Belgian network and one of the following stations: Bruxelles-Midi/Brussel-Zuid, Antwerpen Berchem/Antwerpen Centraal or Liège-Guillemins.
Consult any Belgian Station fares

N.B.:

* In Brussels:
A Thalys ticket departing from or arriving at Brussels-Midi is also valid for any regular (non-Thalys) train to Brussels North, Central, Luxembourg and Schuman stations.
* In Antwerp:
A Thalys ticket departing from or arriving at Antwerpen-Berchem (Anvers) station is also valid for any regular (non-Thalys) train to Antwerpen Centraal station.

well '1 journey' means one destination i would think - not even allowing you to get off at Gent - in any case i do not think it is a pass like a railpass for unlimited travel for 48 hours. Not sure but

1 journey between any - but i do not think this means all.

Just my take.

I'd still like to do a stop over in Ghent. How much is a ticket to go from Ghent to Bruge on the day of travel?

Also for my trip to Amsterdam.

I'm assuming I can buy the same type of pass "Any Belgium Station" from Antwerp to Amsterdam and use the "free Journey" to go from Bruge to Antwerp, no?

Ticket from Gent to Bruges, for about a 30-minute train trip would only be several euros or so i would suspect.

The ABS fare in my understanding of it is only in conjunction with Thalys tickets - so if you take the Thalys from Antwerp to Amsterdam then yes the same ABS scheme would be in effect. But i'll suggest that you could end up paying more total as Thalys fares can be much higher than the normal IC non-Thalys trains running the same route.

www.ns.nl the Dutch railways site should give prices for both Thalys and IC trains Antwerp to Amsterdam C.S. (Centraal station) or www.thalys.com

thalys fares can be cheap if you get one of the elusive and sold in limited numbers fares but full fare is often much higher than the IC trains that run the same route hourly. And there is no ABS fare except on Thalys fares.

Your ABS ticket is valid to Ghent. That is the first station you get off at. It is not a pass for travel through Belgium, but a ticket to one station in Belgium, with no getting off along the way.
You then need to buy a ticket to Brugge from Ghent. It will not be very expensive.
It makes no sense to buy a Thalys ticket from Antwerp to Amsterdam -it take much the same time as the intercity train, and unless you can get one of the really cheap tickets is a lot more expensive. Thalys trains do not run as frequently as the Intercities either. Just buy a ticket from Brugge to Amsterdam via Antwerp, or buy two separate tickets.
You need to check the schedules for Christmas day - there is probably a reduced/Sunday timetable in operation that day.

I found a ABS fare from Antwerp to AMS for 31e - Since I'm booking early, this seems to be a good deal. So the plan is to use my free journey from Brussels to Ghent, pay to go to Brugge. Use the free journey to go to Antwerp, then head on to AMS. This sound right?

It is not an ABS fare from Antwerp to Amsterdam - Amsterdam is in the Netherlands so you cannot possibly use an ABS fare for this - do you mean a Thalys fare for €31, which will include an ABS ticket in it?
Are you sure the ticket is available for the date, and more importantly the time you want to travel? You have to have a reservation for the Thalys and can't just take any train you want. If you are planning on spending time in Antwerp you may prefer the flexibility of the intercity trains as they are more frequent and you can get any one, rather than having to get a Thalys at a set time.

The cheapest Thalys tickest from Antwerp are €19, there are Thalys tickest available on December 25th from €27. The intercity is available from €30.20.

There are 15 intercities that day, and 7 Thalys.

look at www.nshispeed.nl. You will need to use IE - it doesn't work well in Firefox for instance. You can see all the trains and prices there, in English.

A ticket from Brugge to Gent costs 5,90 euro (one way).

hetismij - since the OP has her/his info Q for you or anyone else versed in Dutch trains - the new high-speed line that has been built and not opened between Schiphol and Antwerpen Centraal - i hear it is due to open soon, after a few years delay i believe to get proper rolling stock - anyway the high-speed domestic sprinter trains to run over this route i wonder if they will require reservations a la Thalys? Be more expensive than Ic trains? any insights would be appreciated - most significantly a start up date?

Dank u wel, very wel!