Lets answer one thing at a time..
-Two blown hydraulic hoses under bed, I know they had issues with hoses in 2012 with many brands, all were replaced by Lippert
-fridge can't keep anything frozen much less cold, Are you fans working in the back of the fridge? Is this on Electric and Propane? Propane always works better
delamination in several places, Caulking sealants checked annually?
constant water lines leaking, >> joints leaking or connections or t tape missing on plastic to brass connections<<<
two windows have leaked>> thermopain or water leaks<<
cheapest carpet made I agree but all trailers are the same
poor quality workmanship, >>Define issues<<
needs a new ladder, >> Measure it and check places like PPL Motohomes or RV Surplus in Goshen<<
manufacture can not guarantee what ladder was put on it,
propane hose rupture, >> Happens<<
hot water element went out, >> Ever run the tank dry with element turned on? $10 bucks at Lowes or Him,e Depot<<
air mattress leaked first use (at seams). OK, did you get it replaced under warranty
Manual is useless, you would think they could make it model specific. >> No brand I know provided this, usually a collection of manuals and data sheets from items installed<<
Toilet valve failed>> Ok, replace toilet $120 -$140 bucks<<
drawers will not stay in during travel, finish coming off cabinets. >> Fix them, not really that hard, screwdriver and maybe some needle nose pliers<<
Wiring behind main panel looks as if it's cheap Chinese extension cord ( looks like a rats nest). In general you can tell they don't care how it's put together as long as it stays together long enough to unload it on the consumer. Hoping to find a low bridge somewhere. >> No Comment<<
2012 3510RL >> This trailer is 5 or 6 years old, dome of your complaints are general maintenance<<