One has to be careful categorising players as 'tight' or 'loose' in terms of bvb shoves. Often those players who are loose in the early/mid stages of a tourney are the type who want to see a flop and "hit". However, when facing a shove they have to decide based on the absolute strength of their hand vs your range, a skill which many won't have developed (i.e you deny them the chance to see a flop before committing to their hand). So they may actually call quite tightly against open shoves. Similarly, tight players may open up their calling ranges later because they understand about hand strength (which is why they are tight earlier on) and realise you, as a reg, will likely be pushing widely from SB.
Fagin is right that showdown equity and fold equity are separate concepts. However, I think what noz03 is saying is that, as our fold equity goes down, our showdown equity needs to increase relatively because we get called more often (which is right).
noz03, I think you may have misinterpreted the 'first in' push chart. None of the charts suggest pushing any 2 from the SB. What it says is that for 13bb you can profitably push at least: 97s, 96s 87s, 86s 76s, 75s 65s and better hands from the SB.
Please remember the charts are just a guide. As players improve, ranges will move closer and closer to the unexploitable Nash range.
@noz03, as a guide, clueless players will: a) call you wider than they should in some spots (where they should be risk averse) and b) tighter in others (when the have decent hands and are getting good odds but nevertheless fold out of fear of the unknown).
If players are tight, you can generally widen you range compared with the Nash range. If they are loose, you must tighten up. You are quite right that how much you need to push depends on how much pressure you are being put under. If the SB regularly folds to you when you are in the BB, you can aford to wait for better hands on average to push when you are in SB (i.e not take thin shoves) because your stack is not dwindling.
All the best.