Small Engines (Lawn Mowers, etc.): Mower Belt Adjustment, clutch lever, screw adjustment

Question
Older Ariens riding mower (model RM-830, 927024).  Just replaced the mower/deck belt because it was slipping under heavier loads.  However, the new belt also slips in the same manner.  

I figured I'd probably need to adjust the tension on the belt using the yoke adjustment bolt at the front underside of the mower (near the clutch; also near the steering gear).  It consists of an adjustment cap screw and a spring clip.  The owner's manual describes how to tighten it (excerpt):

"Depress spring clip with wrench and turn for belt adjustment...<etc>.  

Here's the part that I'm having trouble interpreting:

"While tighening the capscrew hold the mower clutch lever so that the front edge of the lever is positioned in line with the rear edge of the forward notch of the quadrant.  Look through the slot in the left side of the cowl to see this.  Belt engagement should occur with the lever at this point.  The lever will pull slightly rearward from this point when the tension has been sufficiently adjusted".

I assume they mean to push the clutch lever forward to a point just before it would normally engage, right?  Also, since this is an older mower the threads/linkage/bolt appear to be rusted solid.  I've tried some good penetrating oil (PB blaster), but no luck yet.  

First question:  Am I on the right track by trying to tighten the cap screw/adjustment linkage, or is there something else you can think of that might be causing the belt slippage (it does work, just not under a heavy load)?  

Next: I'm assuming I'm interpreting the owner's manual correctly in my placement of the mower clutch lever.  Also, I'm assuming that when I push inward with my rachet/socket on the bolt, that it's supposed to depress the flat spring clip just enough to allow the cap screw to turn (if it wasn't rusted).  Am I correct?

Finally, if I'm on the right track with this, and the linkage really is rusted as bad as it looks, what options do I have?  

I admit, I haven't tried a good breaker bar yet (kind of hard to use one without tipping the mower or jacking it up a lot more than I have been), but I've only been working on this for a day.  

I'm looking for the easiest way to fix the problem without major disassembly of the chassis/linkage (if possible).

Please help...thanks!

Answer
Good job reading the manual!  Most people don't even keep it.

Your definitely on the right track.  I would tighten the belt due to other parts, like the pulleys wearing.

Can you clean any of the threads with a wire brush?  Is the part located where you could get a torch and heat it?
Mower parts have a way of rusting tight...I've broken a lot of stuff due to rust...there's rarely an easy method.

Let me know how it goes.
ERic