hit by an uninsured driver in PA, my carrier (Erie) is paying out the single-vehicle UM limit instead of stacking across all 3 vehicles on the policy - is this a "stacking" issue or am i misreading the law?

need someone who actually knows PA uninsured/underinsured motorist law to gut check this because the adjuster is telling me one thing and what i am reading online suggests something different. dont have an attorney yet, trying to decide if i need one.

facts: april 26, i was making a left turn from a stop sign onto a 35mph road in chester county PA. driver coming from my right ran a stop sign at like 50, t-boned my drivers side. police report assigns full liability to him. he had no insurance, license was suspended, car was registered to his girlfriend. no recovery to be had from him personally per a quick judgment search his only assets are a 2009 pickup and an unfiled tax refund.

my injuries: dislocated shoulder, torn labrum (had surgery 3 weeks ago), 4 weeks of PT so far with at least another 12-16 weeks projected, some pretty significant neck soft tissue stuff still being worked up. medicals are at $47k and projected to hit $80-95k by the time PT is done. plus i was out of work 7 weeks ($11,200 lost wages). no permanent impairment expected per orthopedics current estimate but the labrum repair has like a 12-15 month recovery window before we know for sure.

my policy: Erie. 3 vehicles on it - my truck (the one i was driving), my wifes SUV, and our old corolla we kept for our kid. UM/UIM is $100k per person / $300k per accident on each vehicle. premiums were itemized by vehicle on the renewal so each vehicle has its own UM/UIM line item we paid for.

Erie is offering policy limits but only the $100k from my truck (the vehicle i was driving). their adjuster said "PA stacking was eliminated in 1990 unless you signed a stacking election form" and pulled up our policy which apparently has a stacking waiver from when the policy was originally written 12 years ago. i dont remember signing this and neither does my wife but it could be in our old paperwork somewhere.

here is what is confusing me. when i read the PA MVFRL i see the 75 Pa.C.S. § 1738 stacking provisions and the rejection form requirements. my understanding (from one google deep dive) is:

(1) PA does require a SPECIFIC stacking rejection form signed by the named insured to validly waive stacking, the form has to use specific language, and if the form isnt signed or doesnt match statutory language exactly, the rejection is void and stacking applies by default. several PA supreme court cases (Donegal v Sauers, Sackett v Nationwide) seem to have invalidated tons of these rejection forms over the years on technical grounds.

(2) there is also "after-acquired vehicle" doctrine. if you added a vehicle to the policy AFTER signing the original stacking rejection, you needed to sign a NEW rejection form for that added vehicle. failure to do that means stacking applies for the after-acquired vehicle (and possibly the whole policy under some reads). our corolla was added in 2019. truck was added in 2022. policy was originally written in 2014 with just the SUV. so two after-acquired vehicles since the original (alleged) rejection.

(3) inter-policy stacking vs intra-policy stacking: PA distinguishes between stacking ACROSS vehicles on the same policy (intra-policy) and ACROSS multiple policies in the same household (inter-policy). there is also a household exclusion fight that pops up.

if intra-policy stacking applies on my 3-vehicle policy, my UM coverage would be $300k not $100k. that triples my recovery and basically covers all my projected medicals plus actual damages. if there are after-acquired vehicles that void the rejection, even more reason it should apply.

my questions: (a) is the adjusters quick "you signed a stacking waiver" answer typically correct or is this an area where a quick attorney review of the actual policy file would frequently overturn that position? (b) what would an attorney typically charge to review the policy file and stacking forms to see if there is a real argument here? (c) is it worth the contingency hit (typical 33 percent) on the difference between $100k and potentially $300k? (d) anyone gone through Sackett-style stacking litigation in PA recently and have a take on how aggressive courts currently are on this issue?

policy limits are policy limits but $200k of additional coverage is on the table here if the analysis goes my way and i would feel really stupid leaving it on the floor because i didnt push back hard enough on a 20 second adjuster phone call.