Agressive big boa in a bad condition

[Pitonica]

Hi. I have never fed him live but I don't know about the previous owner. He came with a tip of his tail missing (mentioned in the first post here) so that's why im worried it didn't shed right again aldough I keep the humidity well and he has a nice size pool he can soak in whenever he wants. I have a good zoomed shedding aid spray and I will use that on his tail. The rest of him shed fine. Neck doesn't look swollen.To me he looks skinny and too soft when I try to move him, he has more loose skin and less muscle at least Its my opinion, maybe that is because he is an older snake or his immunity needs to improve. He looks better thats for sure. He drinks like a doggy in the first few minutes that I put him fresh water which is every two days or if he poops/pees in there. So he is well hydrated. Aspen works ok for now aldough I would switch him to cardboard or newspaper just to be sure...
I never saw anyone hold him, not even a previous owner so I don't know what to expect, im totally in the dark. He acts curious and calm when I approach him, but when trying to pick him up or hold him anywhere near his first part of the body - he gives the S position and stiffens, than goes slowly right to my hand that holds him. That is REALLY scary cause I don't know will he bite or just see wtf is going on, who are you, you are waarm, don't touch meeeeee, aaaaaaa...(I can almost hear him speaking with the face he makes...haha, so I need 3-4 hands to get him out. The previous owner described him as a scary bitey attacker and as a result he gave him away. If you ask me, this boa doesn't know what a hand is and is scared of any contact resulting him to be defensive, he lacks trust from anyone trying to touch him as he is not used to that. maybe he spent years not being handled. So what I think I need to do is to patiently keep getting him used to my touch and my scent as something positive, than to let him go out of enclosure himself and explore a bit, stretch out, than return him in, as calm as possible, than upgrade to more touching and staying out.
I think he can be fine, just with patience and handeling. The first Im managing, the second would be much easier if I had one bigger snake experienced person by my side. I read tons of info about them and looked at the videos but no study can replace real practice. My heart is in my throat every time his head turns faster to my hands, cant help not to imagine what would he do close to mz head, maybe going berserk once out of the cage.
I will just have to brake the ice and try, just wish he was smaller to begin with
I asked if they can call someone boa experienced to help me but no luck. Only person to help me is the one feeling exactly like me, which is pointless relying on pure luck as this kind of snake needs someone who knows what he/she is doing with no fear in the head.
Usually the more defensive bitey or skittish reptiles I begin to handle end up being my favourite and more tame than others so Im hoping same will be with him.

Thanks guys.
Will update if any change.