Would $100,000 US salary after tax be enough to live good life in HU.

$100,000 a year anywhere would give a very nice lifestyle.
if you are planning on retiring and living out many years on $100,000 I can tell you from experience, it will be gone within 2 years time if you don't have a budget.
You can easily live off of $10,000 a year in Hungary if you don't pay rent and have a tight budget, no big plans on spending wildly in Balaton or college fees, books etc.
If you can invest this sum and get a good return then you may be ok in HU.
Not super cheap here any longer like it used to be. Actually even food stuff cost the same or more then items in the US.
It is over 75 cents a lb. for just bananas over here, in the states they are under 60 cents a lb.
Gas,and all utilities are higher here for the sq. footage of most flats then in the US. Water costs more then what we paid in the desert of Las Vegas per month with our long HOT showers there apposed to the quicky bath/shower experience of the average HU  bath. You might be better off staying 90 days and spending every summer with your boy then actually giving up your life to live here, not so rosy in the harsh winter time.
I understand you miss him allot but in the long run he is used to it here and you being able to send him funds is better then seeing his dad depressed by actually living in HU and not being happy
Your living outside of HU may give him more hope then seeing you suffer over here in person.