It has been a bit since I've done the work, but I recall those 2 long 17mm bolts sucking, but they should come out if the trans/engine unit is dropped low enough or tilted enough on the trans end to clear the inside firewall.
The 3 long bolts do not hold the casing together and won't leak any trans fluid, it is safe to remove.
If you have a long ratchet or breaker bar and a 17mm, stick it on one lug bolt and let it spin until it hits the ground. It'll try to tighten the lug bolt and should allow you to break the 33 ft-lb XZN axle bolt loose.
If the tires are still on it, lower it to get them on the ground, then crack the bolts loose.
You can also try sticking it in gear to have the trans/engine help hold it some, but the diff will still want to break free and spin over.
If you drop it on the ground, it is a PITA as you need to raise it to spin the tire half over so you can get to all 6 of the bolts.
You can also use 2 lugs on the bare hub (no wheels on it) and then jam a bar between the 2 bolts and let the bar hit the ground and stop.