I think this is very far fetched and clearly an attempt to make things fit. First you're excluding Selah, and then you're including it without an explanation, to give one example of what's wrong with this method.

To be clear: I do think psalm 46 of the KJV is significant and that a message was encoded there. This one may also seem far-fetched, but bear with me. If the title of "psalm 46" is included, then "shake" has 46 words above it, and "spear" has 46 below it (including Selah). Except it doesn't fit precisely. If "46" from the title is counted as a word, then "shake" has 47 words above it. So we need to extract the 46, which is the second word. This gives us 2 and 46. If we make that 2 the second character, we get 426. Edward de Vere's supposed death was June 26, or 4/26.

I've seen this type of code before in relation to the whole Shakespeare episode. This can only be significant if 4/26 was a predetermined date i.e. De Vere faked his own death, but there are other hints that that's the case.

If you add 4/21/1564 together (a possible date for WS's birth since all we know is that he was baptized on the 26th and the custom was to wait three days from birth for baptism)

Three days before 26 April is 23 April, and that's also the accepted date of his birth. Of course, 'Shakespeare' had no real birth since it was a pseudonym, but I believe this birthday is part of the legend they intended. What's interesting about this is that he also died on 23 April. A lot of Christian saints have the same day of the year ascribed to both their birth and their death; this was a legend they'd create because the roundness of it would add to the perfection of their lives. This may have been done for Shakespeare too as a joke, further indicating that his life, too is a legend.

I would've loved to refer you to a source that shows that the type of code I described was used elsewhere in relation to Shakespeare, and another one that speculates about the record of Shakespeare's baptism having been inserted. However, I don't have them at hand. I'll include them in a more complete write-up that I will do later. But both are on this channel.