Hi there! Just to add my bit, soaked feeds seem to make a huge difference to skinny oldies - I've known 2 or 3 that have been rescued by soaked grass nuts or similar -Allen & Page Fast Fibre/Calm and Condition/VV or unmolassed sugar beet or alfalfa cubes are all good, (grass nuts are cheap but...
Have just been reading about your trials and tribulations - having once (a long time ago!) been sold a horse that was not what I needed and scared the pants off me, I understand how you feel. I don't know how tall/heavy you are but perhaps your daughter's Haflinger would be able to do some slow...
Quote from the breed website -
"Ponies are shown unplaited, but may have lightly pulled manes and tails. The jaw line and heels may be trimmed, but the whiskers should be left untrimmed."
The breed society are keen that the New Forest is a good allround type of pony able to turn its hoof...
Might depend on how he feels to ride - I'm only 5ft5 (about!) but my boy is 14.2 New Forest but has good depth of girth and solid shoulders so don't feel like I'm sitting on something small! I've known smaller ponies ride like 15.2 and horses than ride like ponies.......good luck!
I like it although it works best as a deep litter bed - it makes a nice bed which doesn't move about too much. I don't think it absorbs as quickly as shavings but is as absorbent in the long run which is why it is better deep littered- the big advantage is that the top layer seems to stay dry...