Well we seem to be going over old ground here.
Hard to summarise without repeating yourself
But again, we've not established that there are not penalties. In fact, it seems to me that the potential penalties are obvious, and would no doubt be administered by the FA and the courts. I've explained above what they potentially are, so won't bother to do it again.
Well you haven't shown anything on the courts, unless you are referring to your "Well the punitive punishment is returning £6m or so to Tottenham and accepting Everton's £4m.", which as I said isn't a motivating factor to accept Everton's offer because it isn't a punishment. The courts cannot award anything other than legal costs against Sheff.
I accept I haven't proven that the FA wouldn't impose a £10m fine, because there is no direct precedent. However, the FA have never fined clubs for probable offences, they only do so when it's totally clear that there has been an proveable offence. Just look at the history of fines that the FA has imposed, and find me one where the evidence wasn't totally clear cut. The burdon is just as much on you to prove that a fine is possible.
FA fines are generally quite small too - teams don't even get fined much for tapping up £20m players - so it's a very small chance of a small fine, well worth taking to try to get the extra £2m.
Additionally, the only solicitor on the forum has already asserted that [if the reality is how you believe it is] Everton have a strong position on this.
Right. As long as both Everton and the player see it through to conclusion, we are in a strong position. If the player gets nervous, and decides to sign for Spurs because it's not worth the hassle, we have no recourse.
Generally, your point seems to be that Sheff United wouldn't do anything unless they knew it was kosher. But clubs break the rules all the time - for example, teams poach contracted players and staff. They know they are breaking the rules, but they expect to get away with it often enough that the benefits outweigh the occasions where they get caught. If the only reason you are convinced that Everton don't have a legal position is that Sheff United tried it, that's a pretty weak argument.