Hi there,
To understand whether Satan is evil or not, or whether God created him to be evil, we need to look at his beginning.
Firstly, yes angels do have freewill. Without question. A third of the angels chose to follow Lucifer, ergo, freewill. God, I believe, created angels to serve Him and to companionship with. They knew God existed because they saw Him all the time. Man was created to choose to believe, by believing though not seeing, (in the physical).
Lucifer was created to be the high priest of God:
Eze 28:12 Son of man, take up a lamentation upon the king of Tyrus, and say unto him, Thus saith the Lord GOD; Thou sealest up the sum, full of wisdom, and perfect in beauty.
Eze 28:13 Thou hast been in Eden the garden of God; every precious stone was thy covering, the sardius, topaz, and the diamond, the beryl, the onyx, and the jasper, the sapphire, the emerald, and the carbuncle, and gold: the workmanship of thy tabrets and of thy pipes was prepared in thee in the day that thou wast created.
Eze 28:14 Thou art the anointed cherub that covereth; and I have set thee so: thou wast upon the holy mountain of God; thou hast walked up and down in the midst of the stones of fire.
Eze 28:15 Thou wast perfect in thy ways from the day that thou wast created, till iniquity was found in thee.
Eze 28:16 By the multitude of thy merchandise they have filled the midst of thee with violence, and thou hast sinned: therefore I will cast thee as profane out of the mountain of God: and I will destroy thee, O covering cherub, from the midst of the stones of fire.
Eze 28:17 Thine heart was lifted up because of thy beauty, thou hast corrupted thy wisdom by reason of thy brightness: I will cast thee to the ground, I will lay thee before kings, that they may behold thee.
Eze 28:18 Thou hast defiled thy sanctuaries by the multitude of thine iniquities, by the iniquity of thy traffick; therefore will I bring forth a fire from the midst of thee, it shall devour thee, and I will bring thee to ashes upon the earth in the sight of all them that behold thee.
Eze 28:19 All they that know thee among the people shall be astonished at thee: thou shalt be a terror, and never shalt thou be any more.
Here we see three things about Satan; 1) He was one of the covering Cherubs on the Ark of testimony, 2) He was also a high priest for God. He had the tabrets in him when he was created for worshipping God, and also was covered with the same stones in him that The Levitical High Priest had on the Breastplate of Judgment, 3) He was in the Garden of Eden, and did evil and was cast from heaven, as is stated in, Rev. 12:4 And his tail drew the third part of the stars of heaven, and did cast them to the earth: and the dragon stood before the woman which was ready to be delivered, for to devour her child as soon as it was born.
Yes, God knows everything from the beginning of time, to the end of time. He knew Lucifer would sin, and that Christ would take his place at the right hand of the Father. God created man to have fellowship with, and for man to believe by choice having not seen, yet believing. For man to have choice, there has to be good and evil to choose from. This is why Lucifer was created. He was not created to sin, but God, knowing he would sin, created him that we would know good from evil. Lucifer and his angels will go into the Lake of Fire because they chose to rebel against God. That was their sin. They knew they were to serve God, they knew God is supreme, there is none above Him, et they chose to follow Lucifer in rebellion. Man, in the OT believed because they saw, and were saved. They had freewill to chose to believe and obey, or not. But greater is he that believes without seeing;
Rom 8:24 For we are saved by hope: but hope that is seen is not hope: for what a man seeth, why doth he yet hope for?
Rom 8:25 But if we hope for that we see not, then do we with patience wait for it.
Joh 20:29 Jesus saith unto him, Thomas, because thou hast seen me, thou hast believed: blessed are they that have not seen, and yet have believed.
The last question is whether God, knowing that Lucifer would sin, should have created him in the first place? A reasonable question, but the answer is yes. If God did not create Lucifer, then where would Lucifer's freewill be? The same applies to the human race. Our heavenly father knows who will believe and serve, and who will not, but we still need to be here to make that choice. Knowing the end from the beginning doesn't stop the journey from happening.
I hope this helps. Sorry for the length.
Maranatha