Bad ride/wobble/shake/tire ware

9 months into owning a w star 4700SF Day cab (first owner op truck). Bought at 500,000km (Canadian here, sorry lol).

Everything seamed good for first few thousand KM. Noticed a lite shake feeling in the seat. Decided to replace mis matched drive tires with Virgin hankook DL12's and At this time I replaced the outside steel rims with polished rims, and left the inside rims, the old steelies alone..other then 1 brand new steelie. Should note I had to get longer wheel studs to accommodate the aluminum rims. Still felt a shake in the seat coming from the rear (more noticeable now).
Shake/wobble, feels like I'm running on Michigan roads when the pavement is smooth..

I use a different trailer daily

Can feel it more when running empty or up to 20k in the trailer, any heavier then 20k it seems to not be as noticeable but I can still feel it.
Does it bobtail
The feeling is always in the seat. Almost like a balance issue..

Now this is what I've done in order with no success, still feels the same from day 1.

Tires and rims (outsides)
U joints
4 rear shocks
Both torque bars
3 axle alignment
Both drive shafts balanced.

Would yall suggest $240 is worth it to balance the tires?
Would driveshaft angle check help?

Noticing the inner part of the tires on axle #3 are starting to cup/ware more then axle 2.

I'm not a rich man, just trying to make it like everyone else. Between slow work and this very expensive problem, it has been extremely frustrating. I'm really hoping someone can lead me to a solution without having to spend $600 ever time I go to the mechanic on something that doesn't get fixed.

Thanks, be safe

 

****forgot to mention
Wobble/shake feeling is most noticeable above 50mph. Very faint feeling going slower then that. The faster I go, the more noticeable it is.

 

Got 8 drives balanced. Not much of a difference