Congrats on your first 5k and hopefully you will be entering more events in the near future.  Participating in races is usually a wonderful method to celebrate training, connect with other runners and keep the motivation going for the next level or challenge. 

Sounds like you are going great with your cross-training and staying cautious with recovery.  I know injuries can be frustrating, but it is always good to look at other alternatives and stay active.  Building overall endurance is different for everyone, but I started weight-training a few years ago and tend to believe that it has assisted.

Of course, the only thing I can totally recommend is choose your footwear, socks, compression gear, vitamins/nutrition/supplements and so on carefully.  Get several pairs of running shoes and rotate them out frequently for workouts so you are not placing stress/strain on the same areas over and over again.  This will make a big difference in avoiding recurrent injuries/problems with the same thing, for example. 

Probably obvious suggestions, but there are a lot of products marketed to runners and you may to just experiment with some of them to find out which ones work best for you personally or benefit your performance. 

There are many generous members here willing to offer their kind advice and share helpful experiences, so you will find plenty of support and guidance. 

Best wishes and many happy miles!