bad leak down numbers and oil usage

Disclaimer;

This is the most babied 912 you will see, It is very well taken care of, it is as clean as the day it was new. It has only seen maybe 20 gallons of 100LL in its 1600 hours. Oil changes, and plugs at 1/2 of the recommended intervals. I was hoping it would pass 2000 hours with flying colors.

During my 100hr today I came up with some disturbing numbers. I'm wondering what the experts think.

The engine is 912ULS, flown about 250 hrs / year, currently has 1606 hrs on it. For the past 2-300 hrs I have been tracking increased oil consumption. It currently uses slightly under 2 qts per 50 hr oil change. The engine has always been run on premium auto fuel, Sport Plus 4 oil, plugs every 100 hrs, oil every 50 hrs.

Today I got low numbers on leak down on cylinders 1 & 3. I have done several runs and tested in-between to confirm it isn't a ring grove alignment situation.

#1- 62/80     #2 - 78/80     #3 - 77/80     #4 75/80

About 300 hours ago cylinder #3 started reading a bit 2-4 pounds lower that the rest. Number #1 has always had good numbers.

A compression test gave me these numbers;

#1 - 149     #2 - 183     #3 - 179     #4 - 177

I put oil on top of the piston and retested but it only raised the compression by 5 pounds.

I am interested in solving the compression issue and oil usage cause.

Am I looking at valve guides, rings, valves, or? Is it worth messing with? 

I can do all the R&R work.