You have a great CN, so you can delay if you want. it takes 2-3 months for the KCC to process your DS260 and then schedule your appointment (which is done a further six weeks in advance). So I wouldn't submit the DS260 in, for example, May next year as you may not get through the background checks in time. But a month or two delay now really makes no difference, unless you are super keen to interview in October.
For us, we knew we weren't interviewing until at least April, so we didn't submit the DS260 until July. We took our time, made sure our details were correct, got all our former addresses sorted. We checked and cross checked our data so that, when it came time to submit, we knew our application was watertight and we would not need to re-open (which is not a big deal, but it is a pain).
As for the police check, make sure to look at this page. If it's not possible to get a certificate, print out the relevant advice from this page and take it with you to the interview just in case:
https://travel.state.gov/content/vi...re-selected/prepare-supporting-documents.html