How do I get my brother (PoA) to respect/discuss Mom's wishes on moving?

Mom has stage 5/moderate vascular dementia, diagnosed 5+ years ago. Since then, she's been living near my stepbrother, 1,000+ miles away - most recently in a memory care facility with my stepdad, who had Alzheimer’s/Parkinson’s and just passed away two months ago. My stepbrother has been their primary/local caregiver - and generously offered to continue visiting/helping Mom until we can get her up near us (he assumed it would take ~6 months due to wait lists).

I’ve got 2 older brothers (we’re not close), one of whom has her PoA (“Brother A”). Mom has been begging to move closer to me for 6+ months - roughly since her husband stopped recognizing her and she had to move from AL into memory care - but my brothers have refused to discuss it with me or her. I've been researching facilities at her request for a few years. When our stepdad passed away, my brothers finally relented and agreed it was time to talk about Mom moving closer to us.

I never imagined it would even be a question where she would live when the time came, since they’ve shown little interest in Mom over the years (other than her finances). When she was first diagnosed, they said they were relieved our stepbrother had offered to take in Mom and her husband, because they didn’t want to deal with the situation; they rarely visit/call, and are frequently out of town and/or busy with family or their high-pressure jobs. I doubt Mom’s location will dramatically affect the frequency of their visits. However, I’ve repeatedly said I would prefer to find her a good facility near me so I can visit with her regularly…at least a few times a week (if not daily), which - because of my job, my 3-year-old daughter, and the possibility of a second child soon - will likely only be possible if she’s closer to me (i.e. within 15 mins).

Last summer, Brother A moved out to this area, which meant all 3 of us now live within a few hrs of each other for the first time in 30 years. And although he had initially agreed to discuss Mom moving here, that never happened - and he flatly refuses to discuss her options, include me in any decisions, or listen to/consider any of the research I've done. (I assume my brothers still speak to each other, but can’t be sure.) He’s adamant that he is in charge, he will do his own research, and he’ll let me know what his decision is. He’s been taking advantage of his position as PoA for some time - at one point this summer, he even tried to ban me from seeing or speaking with Mom. Worse, he's now saying that although he intends to move her closer, she likely "won't be as close to [me] as [I'd] like," solely because he’s PoA and lives roughly in the middle of the three of us, in terms of location. This is despite my offering to take on the responsibility of going to the ER at 2am and hand-holding Mom when she needs more attention. He’s even threatened to sue me for harassment after I emailed him just explaining some options I’d found in my years of research, asking to have a conversation about Mom’s choices, and trying to understand why he clearly doesn’t trust me.

He claims that the two things preventing her from immediately moving are space/availability and finances. None of the facilities I’ve contacted see either of these as a problem. Yet he continues to waste time doing his own independent research (in an area he barely knows, in his limited free time), while Mom continues to slip further in her illness and is getting increasingly depressed/isolated - not to mention adding unnecessarily to my stepbrother’s burden just after he’s lost his father. Brother A has said he doesn't see the urgency in the situation, and that it will happen when he's had a chance to do his own research and make a decision.

I really don’t want to hire a lawyer unless absolutely necessary. Ultimately I only want what’s best for Mom. I’m really angry that they’re refusing to have a discussion or find out what Mom really wants and act according to her wishes. Do I have any options other than filing for guardianship/conservatorship? And if so, won’t that delay her move even longer? I’m grasping at straws here…thanks for any/all feedback.