Rather prorsus or omnino.multum
I think the perfect would be better. By "I kept still" I think Poe means remaining motionless rather than not speaking, otherwise he wouldn't say "and said nothing" right afterwards (that would be pleonastic).silebam/tacebam et nihil dicebam
Also maybe nec quicquam would be better than et nihil.
Better: nec interea illum recumbere audivi.et interea illum iacere non audiebam.
Iacere means to be lying (be in a lying position) rather than to lie down (assume a lying position).
Better auscultans. I also feel like it would be better placed at the end, maybe.audiens adhuc erectus in lecto sedebat
I think it's best to simply say sicut ego feci.- 'just as I have done': I guess technically this is referring to the sitting up and listening; so possible to add sedi et?
I don't really know what it is, actually, but seeing your translation I guess it's some sort of insect?- 'death watches': suggestions here.
If you're looking for something less literal but that would be a more usual phrasing in Latin, you could say nihil motus sum, I think, or digitum non movi.- 'I did not move a muscle': translated literally.
Not sure about that. I'd be tempted to say cor index, but I'm not sure it's ok to use index adjectivally with a neuter noun.Off the top of my head, cor fabulam narrans / cor quod fabulam narrat, etc. Not really sure.