The story is unbelievable but the address exists, it has over 9000 btc and there was no withdrawal from it, if you have most of the private key, for that kind of money it is worth learning some python yourself and writing a program that will check all combinations of missing characters, it is not difficult, you can put something together from ready-made codes on the Internet. Do not give anyone any information about the key over the Internet, even if you use some software, only offline. Good luck.