First I would say that Payplan are a reputable firm. However, they do not do everything as I would like, but then that probably applies to every firm out there. Recently they underwent a reorganisation, which, I understand, resulted in a downsizing on staff resources, since then they have become a little less consistent.
Now, on the pay rise front, your IVA payment, as it now stands, before the rise is accounted for , will increase by 50% of your net increase in income (so, basically, half the rise will be added to your regular payment.
Expenses do need to fall within industry guideline figures, which are not published - as you should claim your actual spend and it will be adjusted if it exceeds the guidelines and you cannot justify this excess. These guidelines are sporadically revised but rarely follow general increases in the cost of living. The last set I have seen was 2015 and, as far as I can tell, they are still pretty much the same !
All that said, it is always a good idea to research anything any firm says --- They have thousands of live cases, all possibly on slightly different versions of the Protocol, so sometimes they might apply terms from one Protocol version to another versions case (if you see what I mean). You, however, only have one case to look at !
You are most of the way through, but dig out your proposal and Chairman's Report and everything will be in there.
Last payment ? If you are on a straight 5 year arrangement, yes, the 60th payment will be the last regular payment, as long as you are not a homeowner. If you are a homeowner, you will have to look at equity release or an extension of the IVA in lieu.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014