TBH if it was me I would... decrease my calorie allowance for the decreased cardio.
Do some pilates, any of the excercises that don't involve putting weight on your food anyhow.
Also seated arm excercises with dumbells, bice curls, hammer curls, tricep work...
When desperate (it was stormy and I couldn't get to the gym) I used my excercise bike with my hands it wasn't the best work out (and was sort of tricky to balance myself the right way to do it. But you can definitely get creative if you need to.
I honestly don't think your going to be getting the same cardio intensity that you are use to from your other workouts but its better to stay somewhat active.
Also for the situps, don't just do what you think of as a traditional sit up, if you can varry it maybe it won't seem as borring? Do them in rotating sets of 8...