In answer to your first question, the witness statement you provided to the police would not be sufficient. Although both are treated as written evidence, an affidavit needs to be sworn and witnessed in front of an authorised person i.e. solicitor, JP, Registrar of the Court etc. In criminal proceedings, a witness's statement is treated as evidence to support an element of an offence and usually only requires the person to sign it. Where it is to be relied upon in court, the witness is usually "sworn in" first and then their statement is tendered as evidence. An affidavit is already sworn and essentially sets out the evidence the writer would be prepared to give under oath in court. Because it is already sworn and witnessed, the court will treat it as evidence. This is why in interim hearings where matters are determined "on the papers", you do not get the opportunity to cross-examine (that only happens at final hearings). When writing your affidavit, use dates, times for events and if you refer to any conversations, state the words which were spoken (at least as best you can). You will annex to your affidavit the FVO that has been made. The affidavit form can be found on the Court's website under forms.
As for what is now happening, it may be that the solicitor has not been provided with instructions to respond. I'm also a solicitor and it is not uncommon for me to receive correspondence only to have my client tell me "don't do anything". I'm not sure of the time frames involved but it could also be that if you have not filed for property orders within the requisite time frames, you may need to seek leave of the court to do so. You have 2 years from the date of separation in a de-facto relationship and 12 months after a divorce is granted. Hence if you are married but not yet divorced, the clock isn't ticking (at least with same urgency).
With respect to mediation, in this instance I would suggest that you file your proceedings for property. You can seek interim orders to the effect that:
1. within 48 days of the date of these orders, the parties are to attend a mediation before an appropriately qualified, mutually agreed mediator or Family Dispute Resolution Practitioner.
2. If within seven (7) days of the date of these orders, the parties cannot reach agreement as to identity of the mediator, then the mediator shall be selected by the following process:
a. within seven (7) days of the date of these orders, the Applicant will provide the Respondent with the names of three (3) mediators or family law mediation services; and
b. within seven (7) days thereafter, the Respondent shall select the mediator or mediation service from that list.
3. The parties are to equally share the costs of the mediation, including the costs of the mediator or mediation service.
4. Each party must attend the mediation in person or by telephone and must make a genuine effort to resolve all of the matters in dispute.
5. At least 10 days prior to the mediation, the parties exchange a Balance Sheet, identifying agreed and disputed assets.
There are other orders you can add to this but the above wording is pretty standard. Although the court may not be willing to make the orders for a while to come, it at least demonstrates your willingness to try and resolve the dispute as quickly as possible. Brownie points to you!
Finally, well done on trying to seek alternative ways to resolve the matter. Sometimes though, a person has no choice. Unfortunately costs is not something you will be able to avoid. You can however share the load by partly self-representing and partly engaging legal representation for specific events. If you were to do this, I would recommend if possible still using the same solicitor because that way all you will need to do along the way is update them on what has happened since the last time you spoke. For example, you can draft your affidavit and have them look at before filing.
As for where the proceedings are to be filed, I'm not sure why it must be in WA. If it is to do where the property is located, you can still file in Qld. If the court deems it should be filed in WA, they can make orders to that effect.