Talking just the main set here, so if that is current threshold pace then rest ~ ok. So aim for total 16 x 100 at TRP (1.29) off 2mins would be good start but slowly reducing that rest period over time would be good as a key weekly session. Id also do things like VO2 sessions (about your 400 pace) so say its around 1:22 pace reps should go off about 2:15-2:30. maybe a distance endurance set say a 20x200 off about 15seconds rest, (make sure it really is aerobic though) but with some take home sprints (sets (I may add 2 of these) of 4 x 50m work here, sprint 10m easy 40; sprint 15 easy 35; sprint 20 easy 30; easy 50) at the end to mix it up; then the other sessions of the week, technique/aerobic / mixed strokes, kicking etc.