For McCallion and Porter I started my save on real world and they are still at Derry with no transfer planned. Maybe it has something to do with the loan starting too early for the game? Their loans were announced in December so maybe thats causing the problem.
For the stadium expansion I've found an article from the Derry Journal that says this
"According to planning documents the demolition of the northernmost section of the Southend Stand will result in the loss of 387 seats while the new North Terrace will add additional capacity of 2,940 (2,910 standing spaces and 30 wheelchairs spaces).
This will result in a net gain of 2,550 spectators almost doubling the capacity of the Brandywell from 3,689 to 6,239."
https://www.derryjournal.com/sport/football/brandywell-north-terrace-documents-show-ultimate-ambition-is-for-7408-capacity-stadium-4170987
Every other article says it will be safe standing which would mean it will count towards the seated capacity. I'm not sure what the current seated capacity is but it shoudn't be too difficult to work out.