Comma help and use of the words AM and Drag

Hi, thanks for helping me, please tell me if the following are correct.

1. I, together with my sister and three brothers,___going to the football game.
am--is--are
I know --is--is for singular use, so is the word ARE correct?The answer is "am." "Together with my sister and three brothers" is a parenthetical phrase and doesn't affect the subject, which is I--and only I.
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2. When James rode on the back of my bicycle, he ____his feet.

drug---dragged---drags
I believe this is talking in the present tense---so is drags the correct word? No. Rode is the past tense of ride, so you need the past tense of drag--dragged.
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In this sentence, "I like swimming," the word swimming is a present participle? or a gerund? I say present participle, is this correct? No, it's a gerund--a noun.========================
All doctors who are not on duty will attend the banquet.
is this sentence correct? OR should there be commas after DOCTOR and DUTY?
All doctors,who are not on duty,will attend the banquet. The sentence doesn't need commas. It's okay as written.===========================================