Most of what you said is the signs I see before my guppies give birth. They do tend to become very lethargic, hanging around the bottom or top, beside the heater. They tend not to eat for a day or two before they drop. I really think you have nothing to worry about. If your not using the trap, make sure you have plenty of bushy real/fake plants for the fry to hide. It is very likely that the mother will eat some/all of the fry. They tend to give birth late in the night, when the tank is dark and quiet. They can hold off the birth or even abort, if they feel stressed. Try and keep stress to a minimum, little to no lights, turn off the airstone..
I have been lucky to see some of my guppies giving birth and have feed her as she is giving birth. I find this reduces the chances of her eating the fry. IMO
, they eat the fry because they haven't eaten for a few days before the birth.
Do you have a liquid test kit. Just test it and make sure the water quality is good. This can be a factor of whether she gives birth. Like all fish, they need good quality water, especially when giving birth.
For the fry, I would suggest leaving them in the 5g on their own, remove the mother. You will need to cover up the filter pipe, with a prefilter sponge or a piece of BRAND NEW pantyhose. This stops the little guys getting sucked into the filter.
I hope this helps you out. All you have to do now is wait!!!!.
If you need any more help, just give me a shout.... Ian