I have a 4-14 4340 Oliver. The furrow levers purpose is to keep the plow level at different depths in conjunction with the hydraulic cylinder depth stops. If You change how deep You go; then its necessary to move the furrow lever. If plowing 8" deep for example. If both the left, & right sides are not equal depth the plow will pull crooked, take more Tractor HP, & flat out not plow correctly.
Also when breaking the first round, I pull the lever all the way down. The second round the furrow will be slanted. The lever is moved to about the mid position, & on the third round I begin adjusting about every 100 feet. Measuring the furrow wall height each time I stop behind all 4 furrows, or in your case all 3. Sharpening shares is not something I do. Its hard to get them even, & they throw the plow off balance if not done right, & again the plow can run crooked.
If You wish I could scan & Email operators instruction; but cant guarantee they would be the same. Although the plows look close!