Building a loft in the garage, plastic Wr trusses, etc.

[Ridderstrom]

Garage L 8.4 W 6.0, H 2.5 m internally, 22 degrees roof pitch. Planning to make a storage loft in half the garage (approx. 4 m) with W-trusses, planning to keep part of the existing ceiling except for the 2.4 x 3 m hole I have made. It is based on a Terraplegel sheet metal outer roof on battens. Soft underroof with eaves ventilation. The underroof fabric hangs down about 4-5 cm. CC 1200 on the roof trusses, 145x45 mm "upper legs." Picture below. Planning to make an air gap with 45 mm spacer and oil-treated board. Then, add on top of the rafters 2x95 mm and insulate 270 mm with regular stone wool boards (3x90 mm) up against the roof. Also planning to hang a 90x90 beam under the ridge to attach, among other things, climbing ropes/Roman rings. A few questions have arisen:

1) Does it matter if the underroof fabric hangs down towards the board in the middle, but it is ventilated on the "sides"? Could set a 45x45 in the roof slope on top of the board but unsure if it serves any function. Alternatively, larger distance to the board and add more.

2) As can be seen, there is a gap left in the underroof up in the ridge. If the board meets in the middle up in the ridge, is the ventilation sufficient? and should the joint between the board sheets in the ridge be sealed?

3) What is required to be able to remove the diagonals in the roof trusses (but retain the "lower legs")? Considered offsetting with glulam beam in the ridge, but I do not want to tear down walls to set up glulam posts and also do not want a post in the middle of the garage. Can a glulam beam that is screwed into the "lower legs" of the trusses on either side of the proposed loft and rests on hammer beam/walls (145x45 mm studs with 60 cm c/c) suffice as a foundation to set glulam posts and ridge beam on? Surely impossible to answer, but is it completely unreasonable or can it work? Existing upper legs can be reinforced with any dimension.

3) If diagonals are retained, there will be issues with the vapor barrier. There will be quite a few diagonals to seal around and also down over the tie beam towards the vapor barrier in the wall + around the beam that is hung up. And it probably won't be completely tight. Is it tape around that is required or can it be supplemented with some kind of sealant? Horizontal or vertical rollout easiest?

Other views, tips?