If you are unsure about the will's validity, you can ask for an affidavit of due execution from the witnesses. However, there is a presumption that a will which on the face of it appears to be valid IS valid, unless it is irrational.
If you have real concerns, you may like to seek the advice of a handwriting expert.
I agree with you about the concerns regarding forgery - I have been working tirelessly through an organisation I helped found in 1998 to regulate this industry. I see wills and probate as open to more abuse than any other area. Given what the probate industry is worth on an annual basis, it staggers me that it is still so open to abuse.