“”Is Salvation available to all mankind?””
If any man repents of his sin and trusts in Christ, he is saved. ANY man. So I think it is fair and true to say yes, it is.
This does not deny the election and predestination taught in Scripture.
“You never heard of his involvement in the murder of Servitus? “
I have heard conflicting accounts about the death of Servitus. I do not hold a fast position on it. I don’t think we have enough information to condemn or clear Calvin on it, honestly. It was apparently done in a lawful manner, but whether those laws were just is another question. While no excuse, the fact is that death for heresy was commonplace at the time. Calvin made have been murderous, or he have made a sinful error, or he may have actually been correct.
I don’t think murderous is quite fair, though, because a murderous person tends to murder frequently. No one has charged Calvin with this. So I think he either made a dreadful, sinful error, or a difficult but correct decision. I am not certain.
“I cannot judge the state of his salvation.”
Well, ultimately, we don’t know any man’s heart. But he did frequently and effusively profess Christ and was a pastor for many years. I doubt he kept up a wearying pretense all that time.
I commend you for acknowledging that Calvin could very well have been a murderer. Not many Calvinists would accept that very real possibility; and to be fair, one must also acknowledge that David was a murderer as well. David obviously confessed his sin of murder. Not nearly as confident that Calvin did the same.