I am glad your garden is doing well Larkspur and sorry about the caterpillars. Are you sure you can’t squash a few rather than lose your plants? AND/OR it should be that after this rain, new growth will save the day – I have already noticed it happening here and we have been taking some well eaten and yellowing leaves off brassicas (to compost) which helps reduce slug numbers and to keep on top of weeds, which often hide under old leaves.
Funnily enough I have few caterpillars at present, on kale and sprouts. Some brassicas have been under mesh and they are certainly the cleanest, next year you could lay mesh on top as in the photo below, the cauliflower under it have grown really well, they are to curd in April.
Cauliflower planted 1 July after garlic harvest – the uncovered plants were more attacked by insects
same view 8 weeks later on 26 August
Re your sprouting, if it is purple sprouting for the spring it should not flower now, but you could try cutting off flowering stems and hope it changes its mind. Another year, try sowing it later, even in early June for planting early July eg after overwintered garlic or early lettuce.