Is there anyone in your department/school who is a Grad student program director (or similar)? Talking to someone who acts in an administrative role for the program could be a way to get insight into how you might proceed. Of course you would want to make sure this is someone with your best interest in mind who would not share what you are talking about with your advisor, and you may need to alter what you tell them a bit. I have experienced issues with my PI, and have received a lot of great support and help from the person who administrates the departments graduate program. They are a wealth of knowledge with regard to funding options, and they have been able to subtly find out funding options with other PIs before I make any big decisions. Also, having someone in this type of position could help ease the transition to a new PI, and keep things as civil as possible. That way the new PI doesn't feel like they are 'stealing' students, and you don't have to burn any bridges.
If that resource doesn't exist, I think it is worthwhile to begin a conversation with the PI you are interested in working with to see what funding options they have, and discussing the possibility of moving to their lab. Staying in a toxic lab environment is probably not a great decision for your mental health and success, and it sounds like your current PI is not someone worth dedicating so much of your time to. I would definitely see about switching labs before leaving your program.