They grow in our yard so we just rinse with a little vinegar water allow to dry and give to the birds occasionally paint with a little Almond butter or Peanut butter and add some pine nuts or sprouted seeds.
Homeopathic Traumeel a 2-3 drops in the water will reduce swelling and discomfort, by the way our avian Vet is the one who says to use a little antibiotic cream it won't harm them if they taste it but will speed healing to keep it moist.
My friend gives her birds a day out one at a time fairly often but she uses a harness and keeps them crated in the car. Her birds have been to parks where she encourages people who show interest in birds to learn more discusses the difficult side of bird keeping. They have also been in Lowes, Home Depot and a Nursing Home or Hospice. Needless to say her birds are well socialized and well trained. To top it off she watches their body language carefully to intercede when the bird approaches the tired zone or overload.
Best advice I can give you is go slow and win his trust, don't rush him Greys in general take their time getting settled in and used to new surroundings, new foods, new toys. All will be changing for the better but he has to decide that for himself, speak kindly and often, offer treats once in a while and just let him get used to the new digs and the new flock (your family).
You also need to try and apply a little antibiotic cream or ointment to the toes it will heal faster with less chance of infection less discomfort, since they do not care what they walk across.
I think this step into a new beginning for you both will pay off with a slow patient approach. The fact that you have limited bonding time after you bring him home may be for the best it will give him time to look about and get used to his new surroundings prior to studying his new human family. Can't wait to hear your stories as he blossoms in you care-hint-pictures would be welcome as well.
We can get Palm Nuts in the USA now. You can also try making a little whole grain pasta to toss with those veggies some ginger and a touch of red Pepper flakes to disguise that Palm oil and it should work.
For the texture and it's ability to push other foods out of the crop often recommended to assit with treating birds who have ingested metal parts. Do try to get oatmeal with out added iron.