These are great arguments. Now let me answer them humbly:
- The word أُحِلَّ does not necessarily mean that something was forbidden before. Consider 5:96. Sea food was never forbidden to Muslims before.
- The phrase تختانون أنفسكم does not necessarily mean they did something wrong; it can mean that they thought they were doing something wrong. It also may mean that because they misunderstood, they may have stopped themselves from doing something allowed and that added an unnecessary hardship on them.
- The clauses فتاب عليكم وعفا عنكم can be understood to mean that God is not reprimanding them for misunderstanding and thus they may breathe a sigh of relief. The word تاب has been used in that sense elsewhere, for example, 9:117.
The verse clearly says that they almost deviated. Thus they did not sin, just were about to. The verse's use of تاب therefore eases the minds of those who thought they had sinned by thinking of deviation.
Also, the word عفا has been used elsewhere to mean "don't worry", for instance, 5:95, which clearly says that the past is forgotten; those who did that in the past need not agonize over it.
Dr. Ahmad Hijaazi As-Saqqa, in his book لانسخ في القرآن, pages 58-59, discusses these four terms. About
أُحِلَّ, he says like I said and gives more examples, such as
اليوم أحل لكم الطيبات "Today, the good things are lawful to you" (5:5). Good things were never unlawful before to Muslims.
As for
تختانون أنفسكم, he presents an excellent analysis of this phrase. First, he says, the word
تختانون is related to خيانة the same way the word تكتسبون is related to كسب, i.e., to make an extra effort at it. Thus, the phrase means "you were trying hard to betray your nature: depriving yourselves unnecessarily from something you are entitled to but thought you were not." That explanation is better than mine and serves the same purpose: they avoided what they thought was forbidden but it wasn't.
As for
فتاب عليكم, he says like I said and quotes 9:117 too and gives more examples, such as,
A person who killed someone by mistake did not commit a sin. Thus the phrase
توبة من الله clearly means a release from guilt.
And finally, in regard to
وعفا عنكم, Dr. As-Saqqa offers two interpretations: Pardoning an infraction, or easing. I humbly suggest that the linguistic meaning of the verb is to gloss over or skip or let pass. At any rate, it means the matter is gone; one need not fuss over it.