If this is a brick veneer cavity wall I recommend not doing it or hiring a design professional.

I can't comment on a loading condition I haven't seen but otherwise your comments seem reasonable. Shore the frame before removing the studs. There is no benefit to gluing or bolting the 2x12's together, just nail them well and secure them at the supports. You can put one 2x12 up at a time if it is easier but make them tight to the framing above. Make sure the bearing is on two jack studs at each end with a full height king stud immediately adjacent. Nail the shortened studs to the beam and to the parallel joist. Check the remaining wall for lateral bracing, you might need to add some at the corners. Make sure there is no opening in the basement wall below the support studs and take the load directly to the sill beam.

Thanks! Yes the wall above the proposed opening is frame construction, no brick, just clapboards. It is one full story and then the attic walls. Again, floor joists are parallel and are not tied into the balloon studs. Would you recommend the double or triple 2x12?
thanks
Tom

I don't like to comment on any loading condition I have not seen but a 9-0 double 2x12 beam will support a uniform live plus dead load of more than 450 lbs per linear foot with acceptable deflection. A triple member beam would carry 50% more load.

It is a good idea to have a knowledgeable person look at it.

I think you should go talk to the building dept. before you apply for a permit and they will direct you in the right direction.
Don't forget there is a load path that has to be carried down to the foundation wall too. Depending on your code there, double trimmer studs are required lots of times with a span over 8'.