Hi
this link should answer both questions. For the manual keyboard liability you need to switch to engineer mode. If you get errors when placing lay bets check you are not laying below Betfair's minimum lay liability
formula for laying percentage of bank liability:
liability%*IF(test_mode=1, test_funds, total_funds)/100)/(lay_price-1)
so if 1% of bank:
1*IF(test_mode=1, test_funds, total_funds)/100)/(lay_price-1)