Having been called for jury service and having observed multiple court cases, including those for rape and sexual assault (both concerning cases from a 'domestic' setting and those not) I am quite certain that one (or a combination) of three things is true.
1) you are either not in possession of the full facts and are missing some rather key ones
and/or 2) you are omitting key facts
and/or 3) you have fabricated all or most of this account.
There is rarely much independent corroboration for an actual rape taking place.
You portray an almost 'ideal' case to prosecute, apparently with there being a plethora of compelling evidence on hand.
I know for a fact that the CPS in England will run a prosecution based on one persons word against an other where there is nothing significant to undermine the case (such as an ulterior motive, witnesses giving different accounts / changing their accounts, the complainant having a history of dishonesty etc)
There must have been some quite pertinent facts omitted from the above account or it must not be a true account of the full facts to explain why the CPS would not prosecute.
The CPS have to peer review decisions not to prosecute in sexual cases and complainants can seek a further appeal after that.
There is no such thing as a witness 'too young' to testify in England and Wales. A witness obviously need to be able to have enough grasp of language to be able to explain what they have seen or what happened to them and the police and CPS will employ the services of dedicated intermediaries to provide assistance for taking video interviews and giving evidence at court.
see here for an example of a very young person giving a video interview
A two-year-old girl is believed to have become the youngest person to give evidence in a UK criminal case, after her interview was recorded by a specialist court team.