Hi kilosius,
Peaks -
Since you're using tape, it's not really a bad thing if the levels go higher then 0dB. +6 is a bit much though. Make sure only your highest peaks hit the red zone. Generally speaking, it's almost impossible to clip a cassete (you need to hit like +10, +20), but it's better if your levels are reasonable.
Reverb -
I checked out the specification for your 4 track, and it's a pretty nice machine, and you can easily use external effects with it. Just patch one cable from the output labeled Aux 1 into the input of the reverb unit, and two patched from the outputs of the reverb unit into one of yuor 4-tracks stereo inputs. During mix down, turn up the aux1 knobs on the tracks you want to send to the reverb unit, and gradually turn up the volume for the stereo channel you used as an effect return. I have no idea what Dalelectro pedals are like, but you can usually find full effect rack-units like Alesis Midiverb for less then 100$ used. I don't know what your budget is, but check out pawn shops and music stores that carry used gear. You can sometimes find great stuff inthere (Pedals and racks).
Good luck!
Oren