You're doing well if you're adding 2.5kg a week to most lifts. That's impressive. It sounds like you've only started this workout program of yours a few months ago? You should see the bench plateau sooner than the squat which will likely allow it catch up to some extent.
I don't know what kind of program you are on, but it seems odd to me that cardio would necessitate limiting yourself to one leg day a week. I would think you could add squats to one of your upper body days without too much detriment. If you are doing a leg day and two chest/upper body days... I'd suggest having your heavy leg day, a heavy chest day... and then make that second chest/upper body day a light day, and throw in light legs as well with light squats and maybe a second leg exercise. Light can be reduced sets or reduced weight, or best, a combination of the two. Adding a second lighter leg workout, will help your leg strength catch up to your upper body strength.
Many lifting programs for high performance sport have O Lifts--Squats--Bench happening as part of a single workout, or spread out over two workouts in a day. Often on 3 day schedule.
Monday would be Heavy Squat -- Medium Clean-- Light Bench + assistance exercises
Tuesday -- Sport specific training + Cardio
Wednesday would be Light Squat-- Heavy Clean -- Medium Bench + assistance exercises
Thursday -- Sport specific training + Cardio
Friday would be Medium Squat -- Light Clean -- Heavy Bench + assistance exercises
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...and it generally is deadlift > squat > bench press, just like you said.