8 1/4 axle inspection.

That 30/35inch pound spec is a turning spec and is the amount of force necessary after the sleeve has been crushed, and the pinion nut torqued into the spec range. In the field,and for a newbe, it is best to obtain a crush-sleeve eliminator kit, if they are available.... because as you say, you may have to pop the pinion in and out several times to get the pattern right. The crush sleeves are supposed to be a one time deal. If you get the pattern too deep the first time, then there is no way to uncrush the sleeve.
Having said that;
I have dialed the pattern in with no crush sleeve in there at all, just paying attention to the pinion preload, to not make it too tight, and then after the pattern has been dialed in, then crush the sleeve on final assembly. I've never had a come-back, doing it that way. I've also,shhhhhhh, reused lots of crushed sleeves by installing a thick shim in there and recrushing that bad boy.

You cannot get an accurate idea of the turning torque with the carrier and axles installed. You can only guess. Some guys get pretty good at it.
Don't guess too tight, cuz that will overheat the oil, with subsequent parts failures.
Don't guess too loose, cuz that will allow the pinion to climb up the ring-gear, make noise, and with subsequent parts failures.
Before digging into this it's a good idea to have a selection of pinion depth washer/shims. Every pinion has an optimum depth setting, and altho the range is small, there is no way, without the tool, to know if your new pinion will want to be installed at the same depth as the old one. So you have to guess, and that starts by installing the old washer for the first try.
Every pinion is marked on the nose with a +/- marking. If your new one happens to be identical to the old one, then you may be in for a quick dial-in. But I've never seen that happen; the odds would be astounding.