Your pal is in a very weak position, he should follow the PO's direction--the PO holds all the cards, your friend none. Your friend should consider apologizing to the PO--as tough as that might be to do..
A durable POA is only valid during lifetime if the person granting the power. When the granting party passes, so to does a durable power of attorney. You need to consult with an attorney to determine what you do and don't have.
On the facts you provided, it appears you have a strong personal injury case agains WM, but there are facts missing that could strengthen or weaken your position. You'll need to sit down with a personal injury attorney to discuss ALL the details. After that discussion, the attorney will be able to advise you what the options are, what the risks are, and what your best way-ahead would be.
You can call your county bar association and request a PI attorney, or you can use the avvo.com find a...
You can refuse to consent. That would eliminate the consent search option. But police have other legal options, and the search MAY legally proceed without your consent.
Jail sentences await officers convicted of planting evidence. I believe your sources are wrong, planting evidence is rare.
To minimize the chances of 'all this' happening, keep your car in tip top repair, keep your tags up to date, obey all traffic laws, don't involve yourself in situations that draw police attention, be...
Some errors are NOT fatal to the case. Some are. Why it took you 14 months to review your own case is hard to understand and you may have missed your window of opportunity to do anything about it by waiting so long. That said, see an attorney IMMEDIATELY and have that lawyer review ALL your documents to determine if, under your state's laws you now have any options. Best of luck to you.