Print the form, sign it manually, scan and send. This is what i did and they haven't come back on it. They accepted it.
The form is restricted hence it cannot be signed electronically.
You could, but unless you have a strong case with document proof that she will return to her home country, you run the risk of her visit visa being rejected.
You probably applied Outland which is why your application is transferred to Delhi and the interview is scheduled in Delhi too.When is your wife expected to travel back to India? If she is at 5 months she is still able to travel and it is unlikely that they will reschedule the interview.