Sorry to hear about your accident. Various versions of this basic question are among the most commonly asked questions in this space. Each case is unique, though, and here’s what I recommend in your case:
Go ahead and reload your plan with an end date that coincides with your September 70.2.
Ignore the first week and start instead with a week of mostly Zone 2 rides and runs that includes one speed-play type of workout and one longer type of workout in each discipline. Nothing too aggressive–the purpose of these sessions is to ease back into the flow of training and assess your fitness.
Once you have this assessment, you can start to build a bridge back toward the training prescribed in the plan. This entails looking at the schedule and dialing back each workout to meet you where you’re at. After 4-6 weeks, barring any setbacks, you should be able to merge back into the plan and complete it as written.
Take the same approach with swimming.