You are not required to submit any bank statement when you are applying for an Oman tourist visa. 

You should upload a recent passport-size photograph in the Oman visa application for Palestine. 

Yes, a Palestinian citizen can apply for an Oman tourist visa.

You should submit a passport-size photograph.

Yes, the Oman visa fee is the same for infants traveling from Palestine to Oman.

You are not required to go to the embassy to apply. You can just apply for your Oman visa online through Oman IE Visa.

Visa on arrival is not worth the hassle as the rejection of visa will require you to cancel your trip and depart the country. Hence, it is better to acquire your visa prior to your trip.