I'm sorry to say that I don't think this comparison constitutes strong proof. I'd love to hear Frank Caiazzo's opinion on your autograph. If it's genuine its a bit of an outlier, and he'd be the one to confirm it.
I have never seen an authentic example of Paul signing the t in his last name like that. Look at the way he writes 'all the best' on that album cover...he writes his t's differently in his writing than when he signs his name.