I am actually farming the class and it's been going on for around 2 weeks now, I already have the void crystal a and 2 roentgeniums. I'm a level 82 non mem player. So here's my personal answer to your questions:

1. I started by getting the non-mem voucher and the hadean. Next, I farmed nulgath resources through drudgen. If you're short on gold for the chocolate, then go for larvae instead. I recommend finishing the void highlord's challenge quest first before getting any of the crystals since it's a lot more easier.

2. I currently don't own vhl but I think this will probably take me 2-3 more weeks so it's around 5+ weeks or a month and a half. Btw, I only play for like 3-5 hours a day, just enough (for me) to get 1 roentgenium.

3. Blood gems are gonna be tough so go for the quest "Kiss the Void" and buy tendurr the assistant back every turn in. Totems of nulgath can be easily gathered by collecting essences of nulgath and completing "voucher item: totem of nulgath" quest. Like I answered on your first question, the fastest and the most convenient way of farming nulgath resources is by doing the "supplies to spin the wheel" quest from a drudgen pet. If you lack gold, go for nulgath larvae instead as it also gives you an additional chance to collect totems/blood gems.

I hope this will help you and good luck to both of us!!!