Since the preload is supposed to be set to the value given WITHOUT the crownwheel and diff in place, you can only guess at a sensible preload anyway. The pinion shaft bearings are taper rollers, wear in these is what causes loss of apparent preload and, I suspect, that this is what is responsible for your pinion flange nut appearing to be loose. You can reset a preload into it, but if the rearmost pinion shaft bearing is worn (which no visual inspection short of total dismantling will show) the crown wheel to pinion mesh will not be correct and may result in noise.
I'm certain that the front bearing race can be removed through the pinion flange hole (once the seal is out) as that is how it is fitted on initial build, but it may be WELL stuck on the shaft and difficult to dislodge. I'd be inclined to try refitting the flange and tapping it sideways to dislodge the race.
The ONLY way to be sure is to replace the 4 main critical bearings and re-set up the diff as per factory. But there's nothing lost by giving it a go as it is, either it's quiet and you've got away with it and saved a wedge of dosh, or it's noisy and will need a rebuild (or another axle) which it almost certainly did before you started! Just, if it IS loud, don't drive it long like that or you WILL write off the CWP too!
Wise words Steve thanks. I am indeed going to give it a go as it is. But if it turns out to be noisy it won’t be driven and I’ll re-assess my options.
I think I would have a better chance of success if I could get the bearing out to be able to fit a new collapsable washer. Wish I had a puller like Richards! But I’m guessing I should be able to do the nut up to the required torque - new washer or not?