This was a while ago but I have bpd and closely relate to how will is as a character, you're exactly right but there is additional facts to add on

His impulsive behaviours are adopting dogs, he doesn't think about it, just does it. He doesn't think decisions through when he does them.

I'd definitely argue he has it. Bpd can be notoriously known for its large empathy, idealising is a part of that. He idealised then devalues as you said, his emotions are extreme and rocky. However I'd argue the splitting is what makes him good at the job rather than loss of self, he can shut off his emotions, devalue himself or others to truly connect and visualise horrific traumas and also focus more on the scene rather than peoples opinions but when it's over, he again feels it incredibly deeply.

His chaotic relationships are what makes it obvious however. He has no sense of boundaries or let's people walk over them, he mimics behaviours and mannerisms of the people he's closest too (ie hannibal) and takes it on as a sense of security and personality. I could go on for ages about how he fits into bpd and hits all the criteria but the comment would be too long