Welcome to the Forum!

As a long time shooter of .45 Witnesses, I can confidently say that your .45 Witness should easily be able to handle a limited amount of +P Ammunition. Mine certainly have.
I have occasionally converted my older Blued 1992 .45 Witness to .45 Super and it's not worn it one bit.
That said, I don't believe that +P level power is necessary in the .45 ACP and can hinder controlability which I consider very desirable in a defensive Arm, assuming that is your purpose for this Ammunition. BTW, I've easily killed a couple of good sized White Tail Deer with Standard Pressure .45 185 grain JHP's with only one round each.
However, I understand you may not be at the luxury of being able to pick and choose what Ammunition you can use. These days it's use what you can get your hands on.
IF the round will feed reliably in your Pistol, then by all means it will suffice for your defensive needs.
One very nice thing about the .45 Witness is that it's not at all fussy about what proper .45 ammunition it will feed.
But still test-fire anyways, as you don't want your chosen load to be the exception to the rule, when things go horribly wrong.

Older (1992) Blued and Newer (2004) Wonder Finished EAA .45 Witnesses