lots of questions here.
1, check to see if you do indeed have enough fluid in the rear compartment for hyds and rear diffy.
2, do you actually have a thermal start aid or not? ( not glow plugs ).
3, yes, there are screens.. but lets look at #1 first.
4, on the draft. if you have 2 levers in a double quadrant, you have an adjustable draft control. I have seen these on the X600 and up.. but I'm not sure on the 3500. If you have a single 3pt handle, and then a separate small short lever ont he lift cover, it's either draft on/off selected, then use the 3pt lever for setting sensitivity.
LASTLY, if you do have plenty of fluid.. see if it is dirty or wet... either can cause things like control valves and unloaders to stick, in addition to wet oil having frozen chunks inthe winter, and water vaporizing in a pump to cause cavitation.