OH Dear, if you were to gate his room you would likely have very loud screeching instead of fussing and crying. Feeling imprisoned, trapped. My gut says that would not be a good idea.
Do take him back to his room, without being in bed with you...and yes, without talking.
Actually, at first I would say something like, you need to go back to your room and sleep in your bed. Then talk no more.
Have a chair in his room, sit in it without talking , returning him to his bed if he climbs out again. Do this as many times as it takes. The first few mights it may take as much as an hour or more. Maybe even two hours.
This may take a few nights, perhaps a week if he is very strong willed.
It is important that you stay calm. He will pick up on any nervous tension you are feeling.
If you persevere, if you are consistent, he will get it eventually.
If he were mine, I might suggest a night light , tell him it will help him stay in his bed, take him to the store and let him help pick one out. Very dim one , I should think.
Or if you are financially able, even bedding. Special sheets and comforter or blanket. It will help him to "own" his bed.
Perhaps he was not quite ready for a bed. Some are not until they are three. But you would need to ask someone a lot wiser than I if putting the crib back up is a good idea. My instincts say no, not after two or three months.
In the daytime talk with him. Explain that everyone has their own bed to sleep in. Now that he is a big boy and a big brother it is time for him to sleep in his own bed too.
A tincture of time and patience is needed in this situation.
Remember L., you are the parent, the authority. It is important that you assume that position early on in their lives.
Best wishes dear, and God bless
Grandmother Lowell