There is nothing wrong with wearing dakos peshutos. They are just less durable than gasos. I recently checked a pair of peshutos made in Europe before WWII which were in beautiful condition, both batim and parshiyos. If you get my email address from the mods I will be happy to check this man’s tefillin at a discount and make any repairs needed. If parshiyos need to be replaced we can talk.
Regarding the bracha, unless you see something obviously wrong on the outside, you can continue making the bracha on chazaka.