JohnDB - the Westcott and Hort controversy is NOT a Calvinist vs. nonCalvinist issue. Let's NOT got there in this thread.
As to the idea that Hebrews was written to the Pharisees, I hardily disagree. They were not Christians. There is nothing in the text itself saying it was just to the Pharisees. And I doubt the Phraisees are the ones referred to here:
Hbr 3:14 For we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end;
Hbr 6:1¶Therefore leaving the principles of the doctrine
of Christ, let us go on unto perfection; not laying again the foundation of repentance from dead works, and of faith toward God,
Hbr 6:9¶But, beloved, we are persuaded better things of you, and things that accompany salvation, though we thus speak.
Hbr 6:10 For God [is] not unrighteous to forget your work and labour of love, which ye have shewed toward his name, in that ye have ministered to the saints, and do minister.
Hbr 6:11 And we desire that every one of you do shew the same diligence to the full assurance of hope unto the end:
Hbr 10:19¶Having therefore, brethren, boldness to enter into the holiest by the blood of Jesus,
Hbr 10:20 By a new and living way, which he hath consecrated for us, through the veil, that is to say, his flesh;
Hbr 10:22 Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water.
The letter is written to Hebrew Christians. It shows how the New Covenant is tied to the Old Covenant and how Jesus is the better than the angels, and was the better sacrifice made with better blood offered in a better santuary and is a better Mediator and High Priest - and that His sacrifice removes sin and doesn't just cover it. He fulfilled the Law.
As for some references as to who it is written to:
Matthew Henry:
"The design of this epistle was to persuade and press the believing Hebrews to a constant adherence to the Christian faith, and perseverance in it, notwithstanding all the sufferings they might meet with in so doing. "
Check
this:
The Pharisees were not persecuted - they persecuted. Saul, before he was Paul, was a Pharisee and persecuted Christians.