The food icon in the top left is, essentially, banked food. Your colonists cannot directly eat that. The only way to access banked food is to use a Nutrient Paste Dispenser. If you don't have access to one of those (Solar flare, power issues), you will need to harvest plants such that there is food lying on the ground for the colonists to eat.
I did some testing with the developer tools and here is what I found.
To capture an enemy, you first need to have a downed enemy in the map (duh!). You then need to build a prisoner bed on the same map as that enemy. You will be able to capture him and put him in the bed or a sleeping area marked for prisoners.
At this point, you can wait for your people to give him some basic heal. Once you did that or decided that his life is not worth that much to you (which you should consider since he wanted to kill your friends), you can right click on him and you will have an option to carry him outside the area. This will create a new caravan with the prisoner and his personal transport (aka your friend). You can make him move anywhere you want just like a regular caravan.
Once you bring the caravan to your colony, you have to be careful to capture the enemy once again (this is your second shot at thinking about the value of his life). It seems there might be a bug that drops him on the ground when the caravan enters an area. You should be able to capture him once again.
I noticed a few bugs while doing this.
- Sometimes, you cannot re-use the prisoner bed after carrying someone outside of the area. This is fixed by marking and unmarking the prisoner bed.
- Sometimes and after some time with the prisoner in the bed, you will not be able to carry him outside the area. I did not find a workaround other than not waiting after healing him, or simply not healing him.
It does not seems this is currently an expected behaviour in the game but it would be nice to have those few issues fixed or have some new system that do not force you to put them in a bed immediately. Healing the prisoner is still a good idea so I don't mind placing a bed.
Also, I did not test while attacking an enemy base, only during ambushes, but I think that you can do the same thing.
EDIT
I did some more testing and the same thing happens when you are attacking. It also seems that when you form your caravan, prisoners will follow you if you select them in the caravan screen.
Best Answer
TL;DR
Losing one hand doesn't effect the colonists base ability to aim/shoot the weapon. Losing a hand will only effect their manipulation. Losing two hands still doesn't effect the aiming and shooting time but they can no longer wield a weapon. As long as a colonist has one hand, he/she can use any weapon as usual.
Long
I did some research into the question and ran some tests to see what effects loosing a hand has. The the current effect of loosing one hand is removing 50% of total manipulation. Loosing both hands completely removes all manipulation. When testing this the colonist dropped the weapon and could no longer pick up any weapon.
The colonist with one hand could still use all weapons but only has 50% manipulation. This has no effect on the aim/aiming time of the colonist. I tested this with both colonists and neither of their accuracy or aiming time stats where effected with the loss of hands. This stat can be seen in the information panel.
I've included some screenshots below showing the results of my tests. I did this via debug mode.
Screenshots
Rimworld Tests