vdb and alt

this shit was so fucking weird and after all the reddit posts ive read about it i feel like im the only one with these questions. someone please have an extensive conversation about this with me and take the time to read this. firstly, what did brigitte want with alt. i know, ive read it 100 times that she wanted to side with alt or gain knowledge about how to pass the blackwall, but when we get there, she forces v to pass it, and as v when you ask brigitte if she ever intended to help, she says it doesnt matter because v is about to bring all to its end. what does that mean? why is she implicating that they are all about to die? i thought brigitte was there for information, not to just project her consciousness into the blackwall and stay there from that point on. and why does v agree to all this at the blackwall? he tells brigitte i guess i have no choice, but why? if before crossing it is revealed to v that brigitte never intended to help, why doesnt he just refuse to pass and not talk to alt? what leverage did brigitte have over v right there? and then when all is said and done after v and johnny talk to alt, they all wake up, so why did brigitte tell v that he would be bringing an end to it all? and there is mention of a deal that brigitte made with alt, and to my knowledge, v was not there to see or hear this deal being made. i read that the deal was to let v go safely and alt would help the vdbs but when tf did that happen? and again, what power did they have over v? why was he obeying??? just felt like there were a bunch of gaps while the story for this quest was being told.