I'm not trying to be a dick, but no one here is going to be able to answer your question in a very satisfactory manner. Here's the reason why:
Your proposed race is immune to negative-energy type damage. This could be insanely broken or useless, and this all depends on how prominent negative-energy type damage is in your game. Does one class use it exclusively, or even just integrally? Then if so, making a race immune to their most important damage type is going to be broken. If there's not that much risk in your game that comes from negative-type damage, then this might be a fairly balanced feature for your race.
Your proposed race has a set of vulns and resistances. Once again, the importance of these in a balance sense depends entirely on how these damage types play into your game. What you should probably think about is this: are the net gains (the imms, resistances, and buffs that come from selecting this race) minus the net costs (the vulns, debuffs, et cetera) equal to every other race that is currently in the game?
Same thing goes for the potions and food. How important are potions in your game? How important is eating and drinking?
If your answer is that this race seems to have a higher net benefit than other races (if this race's benefits outweigh its costs in a more noticeable way than other races'), you've made an unbalanced mechanic.
I think what Oliver is trying to say that balance is not singular or even linear. You need to factor in everything together (i.e.: list all races).
The importance of those immunities and everything else is really mute. The reason why is because balance is not based on the cool or not so cool things one race has, but how it stacks to all other races. So, you can't really say, "Immunity to negative-energy is unbalanced" if almost every race has the same immunities. Together, everyone may be balanced, but looking at just one race may seem broken etc.
Personally, I balance most everything in Excel using rating/point systems. It allows me to set budgets for certain systems or even sub-systems. That way I can balance everything together and adjust them accordingly. Like for example, if one Race changes, it may impact more than just itself like throwing a pebble into a quiet pond.
Balance is a circle, not a point or a straight line.
another thing to take into account in regards to balance… is the class is only as balanced as the player is… if the player is a skilled mudder then the class could appear to be overpowered, if the player is an unskilled mudder the same class that appears overpowered on the skilled mudder, could appear to be very underpowered. Balance in MUDs is a very fine art to get 100%
On my MUD we tried to rebalance stuff using a spreadsheet, and released this spreadsheet to the players so they could get some kind of idea how the mud was balanced!