Online Teaching Classes and Presumptive Taxation

Sir,

I take online veda/sloka chanting classes and my income is approx 30k-40k monthly from various students by online transfer to my account. I have other source of income also from FD and house rent.( I am a retired person ).

I have the following queries 

1. Will the income from online classes will come under Presumptive Taxation and if so can I opt for 50% of the total as income earned ? Or should it be Total income - expenses ?  Two other teachers are also supporting me for which I pay them monthly as professional fee.

2. Which form should I use ITR-1 or ITR-4 ?

I am at total loss as I get various opinions .

Thanks in advance.

Viswanatha Raju