Both Mg2+/Ca2+ INHIBIT TRYPSIN. EDTA is a Calcium chelator which will "mop" up the remaining divalent cations so that Trysin can do its action.

In my opinion, having too much EDTA will not affect trypsin action for digestion. Though it is unnecessarily extra concentration of EDTA but it should not hurt.

The ionic strength of 0.5 M EDTA (usually the Na4 salt) is very high (equivalent to 5 M NaCl). That might cause inhibition of enzyme activity. I don't know if this is true for trypsin.

I appreciate if you provide any supporting reference, Dear Adam

The literature in which to find this type of information is bound to be quite old. I found this paper:

http://jgp.rupress.org/content/jgp/44/6/1103.full.pdf

It is a little hard to understand because of the choice of units. In Figure 1, which is for NaCl, the x -axis is the square root of the ionic strength. The y-axis is an expression of the rate at each ionic strength relative to the control rate, in the form of the log of the ratio +1 (so a value of 1 means that there is no effect of ionic strength, and a value of 2 means a 10-fold enhanced activity). Trypsin is the lower curve, and you can see that the activity decreases as the ionic strength increases above a certain point, which is about 0.2. Figure 3 shows similar modest effects for other common salts. Interestingly, ionic strength had the opposite effect on chymotrypsin. This makes sense to me from the perspective of the substrates of these two enzymes. Trypsin recognized basic side chains (Lys, Arg), so ions may compete with the substrate or reduce dissociation of the cationic substrate from its anion. Chymotrypsin recognizes aromatic side chains. High ionic strength would favor binding of the hydrophobic substrate.

Binding of calcium ion to a loop on bovine pancreatic trypsin stabilizes the enzyme but is thought not to otherwise affect the catalytic rate. Here is a link to the abstract. Chapter Structural Calcium (Trypsin, Subtilisin)