No – the strata manager cannot just decide to chair the meeting, it is up to the owners. As a starting point the Chair of the owners corporation chairs the meeting, if they feel that they can’t or don’t want to for whatever reason then they can ask someone else to do it (it can be another owner), and the owners then have to agree.
This is a reflection of a more general issue with some strata managers – it is not their scheme, the scheme belongs to the owners. The strata manager is employed by the owners to do certain things, and the owners set the boundaries. This needs to be made clear – in some cases there is a conflict of interest, such as when the owners corporation may wish to change the strata manager, and in such a case why would you have the party who has an interest in the outcome presiding over the discussion?
Similarly, it is not acceptable for a strata manager to cherry pick agenda items for the AGM, which does occur. If an owner puts up a valid agenda item, then the strata manager must put it on the agenda.
Who is the current Chair of your scheme? If you haven’t already spoken to them, are they aware you are putting up this agenda item?
In relation to the junior strata manager signing the minutes of the last two meetings, it is irregular, the actual Chair should have signed them, but as long as the owners resolved the minutes were true and correct it is not a major issue. Note the owners can resolve that the manager sign the minutes.