ᐅ Wall opening: Steel beam supported by columns

Good evening everyone,

I have the following question:

I am planning to remove a load-bearing 11.5 cm (4.5 inch) thick solid lime sand brick wall.
For the opening of 3.1 m (10 feet), the structural engineer specified an HEB 160 beam, but he is concerned that the brick might give way under the weight of the beam. Therefore, he recommends using a 60 mm (2.4 inch) square steel tube with 160 mm (6.3 inch) top and bottom plates as support on both sides.
I would support the ceiling on both sides of the wall, then chisel out the slots for the supports and set them on the concrete base and anchor them. Then chisel out the slot for the beam, place the beam, and fill the space above with mortar (Is this the correct procedure so far?).

Now my actual question: How can I ensure that the beam and the supports are aligned straight and at the correct angle to each other? I would have the supports welded— or do I have to hope that everything is done accurately and that the parts will just be “laid together as they come”?

Thanks and best regards
Pascal