Whiskies...First, for rear driveshaft length, you need to see if the shaft is long enough for the coupler splines to be safely engaged when the rear axle is at full drop. (Allow for additional drop when the axle is articulated.) A quick check without a chassis hoist would be with jack stands supporting the rear of the chassis. Let the axle sag or hang naturally; disconnect the driveline if necessary. The goal is to make sure that the driveshaft, if attached at full axle drop, is not hyperextending. Spline engagement must be enough to not stress the splines or have the shaft come apart!
As for angles at the rear shaft joints, the CV angle is immaterial unless extreme, since one joint of the CV cancels the other joint at the CV coupler. For the rear axle end, your concern is the pinion shaft angle. Rolling the axle (pinion shaft) upward is to reduce the driveline slope and rear U-joint angle. You must not raise the pinion shaft to the point that the driveshaft to pinion shaft angle becomes zero. If you do so, the bearings in the U-joint crosses will not rotate adequately, and the joint will fail quickly.
So, the goal is to get a slight angle between the driveshaft (tube section centerline) and the pinion shaft (a line extending directly from the pinion shaft). On a lifted vehicle with a CV driveline like yours, the angle between the shaft tube and pinion shaft centerline works well around 1.5 to 2.0 degrees. These measurements are with the vehicle's full weight at curb height, either all four wheels on the ground or the vehicle setting on four uniform height jack stands.
Before stressing over a slightly greater rear joint angle, consider the front axle. Caster, as you suggest, dictates the front U-joint angle. In some cases, the front axle's front joint angle is over 2-degrees to allow for proper caster angle. (Caster often gets ignored on lifted vehicles to reduce the U-joint angle; I always use the factory recommended degrees of positive caster.)
Note: Due to front driveshaft length and the front output yoke location on the transfer case, the front driveshaft's slope angle is typically less severe. A Jeep CJ or Wrangler has a shorter wheelbase than an XJ Cherokee. The CJ or Wrangler rear driveshaft is shorter. In your case, the rear driveline is as long or perhaps even longer than the front shaft due to the longer wheelbase.
This factory procedure (below) for the 1994 XJ and YJ will help demystify your driveline measurements. As noted, the axle/pinion shaft rotation is with steel tapered shims that have slots to clear the spring center bolt. (Do you have tapered shims with the lift kit installed?) At the correct U-joint angle setting, make sure the spring center bolt heads reach through the tapered shims (one tapered shim at each side) and seat properly in the spring perches of the axle:
XJ Cherokee U-joint Angles.pdf 2.25MB
Note that if you do need to rotate the rear axle/pinion shaft upward, you will also be moving the rear U-joint yoke closer to the transfer case. This may work to your advantage if the rear driveshaft is too short now.
As a footnote, you don't want a driveshaft to be too long, either. If the splined coupler is collapsed fully at vehicle curb height, when the axle housing rises, the collapsed driveshaft has no room to shorten. Transfer cases have been known to break apart when the collapsed driveshaft drives forward.