ANSWER: I'd sure like to know which Bible teacher taught this, or which Bible he was using. The scriptures you gave me indicates biblical illiteracy, and possibly his desire to terrify unwed parents.
There are only three instances of the word "bastard" in the word of God.
2 No one born out of wedlock (the KJV uses the term bastard) or any descendant of such a person . . . may be included among the Lord’s people. (Deuteronomy 23:2)
A mixed race (the KJV has 'bastard') shall settle in Ashdod . . . (Zechariah 9:6)
8 If you are not punished . . . it means you are not real children, but bastards. (Hebrews 12:8)
In the Bible's Old Testament, a person was a bastard if their mother was a non-Israelite (heathen) regardless of whether their father was an Israelite or not.
Easton's Bible Dictionary defines the Biblical term "bastard" as being synonymous with the word "polluted." In Deuteronomy 23 the term is used to simply mean offspring that are illegitimate. In the book of Zechariah it is used as another reference for a foreigner. Finally, Paul's use of the word in Hebrews 8 was meant to convey the idea of a group of people who don't share in the same privileges as those who are converted.
The reference from Judges 11:1-3 was not God's doing. Gilead fathered Jephthah by a harlot, as well as sons by his wife. When they grew up they chased Jephthah out of town because he was "the son of a strange woman" (verse 2). If you read the rest of the story you'll find their fortunes changed, and they called Jephthah back home to be their leader.
Finally, you asked about the meaning of 1Samuel 20:30, where King Saul is angry against his son Jonathan and screams at him some very unkind words. He yelled at his son and said 'How rebellious and faithless your mother was!' (1Samuel 20:30).
God had no part in what Saul said in 1Samuel 20:24 - 34. This was Saul's frustrated and angry tirade against his son whom he felt was siding with David (which meant against him). In today's language, Saul's statement to Jonathan would have the same meaning as "You son of a bitch." He accused Jonathan of favoring David over the king.
Our Creator is, without a doubt, no respecter of persons. The apostle Peter, a Jew, was speaking to a group of gentiles when he said that God does not respect one person over another but rather accepts anyone who is willing to listen to Him and do his will (Acts 10:34-35).
Gentiles, of course, have no choice as to who their parents are and neither does an illegitimate (born without the benefit of their parents being married) child. The apostle Peter, however, reminds us that if ANYONE, regardless of how they came into the world, fears God and does what is right, that they will be accepted. The nature of a person's birth has nothing whatsoever to do with whether or not they are ultimately saved. Being born out of wedlock does not matter, what really makes a difference is whether a person has a close and intimate relationship with our Father in heaven.