Your first IF will probably never run unless the lux changes right at 5:00 AM. You'd be better off doing that one as Time between 5:00 AM and Sunrise -45 minutes to capture those events.
Also, if I understand the rule correctly, your intent is that if the lux is below 4500, you want the cabinet lights on unless it's a weekend and only between the hours of 5:00 AM and 8:30 PM and at 8:30 PM, dim to 50% and then when the mode switches to Night, Sleep-In or Tom's bedtime, to be off. Correct?
Here's the way I would do it. The first IF covers bright, sunny days, away mode, night time, and weekends. The sub IF covers your time range of 5:00 AM to 8:30 PM for full lights on dim days. The ELSE IF there covers your 8:30 PM set to 50% level, except when the mode is away, night, sleep in, and Tom's bedtime.
Note that this rule will ONLY trigger if the lux changes. The way to fix that is to add two time triggers to the rule; One at 5:00 AM and one at 8:30 PM. That way, it doesn't matter if the lux hasn't changed, the rule will still fire off and change as you need it to.
I haven't tested this (as I don't have a lux device), but I think it should work.
IF ( ( Illuminance of Lux Reading is > 4500 ) OR ( Mode in Away, Night, Sleep In, Toms Bedtime ) OR ( Day in Saturday, Sunday ) ) THEN
Dim: Under Cabinet Lights: 0 -> fade: 10
IF (Time between 5:00 AM and 8:30 PM ) THEN
Dim: Under Cabinet Lights: 100 -> fade: 10
ELSE-IF ( Time between 8:30 PM and 8:31 PM) THEN
Fade Under Cabinet Lights down to 50 over 1 minutes with 10.0 seconds interval