Wills are - essentially - private. Often the contents are completely unknown until the person dies. So how did you find out? Did your father tell you or did you find a copy at his house? (Or did his solicitor show it to you?)
Your father is the solicitor's client, not you, nor your wider family so there is no obligation to discuss your father's affairs with you, in fact it would actually be wrong to do so. (Imagine how you'd feel if your solicitor disclosed your affairs/decisions to a third party!)
Having said that, I completely understand how angry and upset you are. For the family home to be cleared and sold without involving you seems incredibly hurtful but the solicitor is just doing the job they were appointed to do. Don't forget, your father may have appointed a solicitor to be LPA (rather than you) to save you the trouble! You assume his intentions were 'skewed' by his dementia and you could be right but it doesn't mean he was being malicious in any way. He might have thought 'my daughter loves dogs - she'd be really pleased with this bequest!' without giving a thought to the fact that you would get less as a result. People with dementia often don't think things through although this doesn't mean they didn't have capacity at the time. (Let's be honest, some people make poor decisions all their lives... but they are legally entitled to do so!)
My suggestion is to go see a solicitor yourself (you can get a cheap fixed-fee interview) and tell them the situation. Ask their opinion as to whether you should challenge it. I don't see how you could challenge the LPA as the solicitor seems to be doing as they should. Challenging the Will would be very tricky, not least because judges only rarely overturn wills (and nt tyo mention that your father is still alive!) and that tends to be where there is a huge and obvious error. (I've been through this with my boyfriend's father's will and his step mother and believe me, fairness does not come into it. It's also hideously expensive and you could lose any 'gains' in legal fees.)
I'm really sorry this has happened to you but as I said in my previous post, capacity for making decisions in the early stages of dementia is a very grey area. It's a fine line between saving someone from their own stupidity and trampling on their human right to do stupid things.