1) In this example you identify the advantage of riversa mezana as it is described in Fiore. However, the person covering should not cover in breve, as breve is a centered posta and leaves the outside line entirely open (he will be by the cut). He should cover through a rebatter (setting aside action) or in frontale, which will entirely cover the outside line and give the person covering complete access to his opponent's outside line. Fiore shows this play, and advises the person parrying to make full use of the inside line, stepping inside and using his sword to throw the opponent.
2) Your second example correctly identifies the fact that the dritta mezana will arrive at incrosada with the point off line if the cover is stronger than the cut. The same rule holds true for the cover (not breve, but rebatter or frontale). The this play is included in Fiore, and the person cutting strikes lightly to allow the cover to over-commit, then turns his sword into the now open line, covering the line with his sword and taking his own blade in his left hand to deliver a thrust. This play is called the "punta falsa" or "punta riversa". It takes advantage of the phenomenon you recognized concerning the point at incrosada.
So Fiore saw both of these eventualities and created a play to cover the action the scholar should learn. When one realizes that all the options are included in the plays, then one has only to get very good at them and execute them when the proper circumstances manifest themselves, and learn to flow from play to play.
It's a beautiful, absolutely complete system, as he does this for hand to hand combat, knife, sword in one or two hands, armoured sword, pollaxe, spear and horseback combat. Every play teaches a concept which is part of a coherant system.

