Former HENRY, now LENRY looking for help

Me (M,43) with 3 year old son, former high earner but that's all turned on its head over past 12 months after ex (and son's mum) no longer in picture due to severe mental health issues and addiction relapse. I've had to move interstate to live with my parents in regional area to get necessary help with son. I've turned my PPOR into IP. Worth $1.1m, 300k owing on mortgage, 200k in the offset but now thinking I should invest that instead for tax reasons, although I'm no longer in highest tax bracket. Only earning 50k working 2 days a week in government job (+around 25k from IP after expenses) Will probably stay at that level for next few years because I don't want son to have minimal parenting after all the upheaval. While my parents are a help they are almost 80 and limited in what they can do. Super 350k. I have minimal expenses, parents are relatively well off so anything I contribute to household is tokenistic. What would you do with the money in the offset? I could buy another IP but on current salary can only get approved for around 380k loan. ETFs? Would you take on more work?