Einherjar is soloable, but if you don't finish the entire wing within 10 minutes, you'll time out and won't get full ichor. If you don't want to time out, you need 6 people. I highly recommend reading/liking
this.
Not sure about trust in salvage? Some zones are soloable by a passable Mnk/Dnc (not sure about other jobs, sorry). You can zoom through a zone just getting unlocks and killing bosses, and get a linen pouch( or rarely two) in 15~ minutes.
Alex has become a lot more abundant on Odin at least since the removal of the 3 person requirement for Salvage, sitting at 9k opposed to the 18-20k people were paying late last year.
Nyzul is do-able with 3. I did it with myself, a dual box lamp mule, and a mnk, and was able to get 5-10k a run depending on lameness of floors.
A lot of the assaults are easy and soloable, some you're going to need a few helpers for. Read before you go in and use your best judgement.
ZNMs are stupidly easy now, shouldn't have any problems there.
If you don't have the beastmen kills, I'd work on those asap. Can take weeks to get. If you still need these, I recommend working on Nyzul in the meantime until you can start assaults.
My boyfriend and I (with a caster mule) were able to dual pretty much everything required, with the exception of having to shout for people for ein, and needing some extras for PW.
Ilvl gear makes all the requirements pretty easy, and as long as you have some sort of steady gil income coming in (or lots saved up) it shouldn't take longer than 2-2.5 months depending how many tokens you need and if you're done with the initial requirements. Good luck :3