Quirky 2002 Altima issues

Hello...I really need some advice. Some
background info first. My Dad passed away in
August of 2012 and I wanted to keep his car,even
though he had issues right off the lot with it.

3rd generation Nissan Altima 2.5 4 cyl SL
I got it in Sept of 2012 with 130,000 miles and
have just about replaced everything
(EVERYTHING)except major parts such as
Engine,Trans and Exhaust system. 
Now in 2016 it has 171,000 --I am having issues
with no heat/windshield defroster,as well as a
Revolution problem. It is winter here in NY and I
need the heat and no ice on my windshield.
Here is the weird part: The heat/defroster seems
to work perfectly only when I'm driving and at
40mph-60mph???

The issue with the Revolutions is fairly new. I have
replaced sensors to try and get my SES light to go
out. Could that be related? When i drive and let my
foot off the gas to coast the car juts forward a little
just once with the Rev needle jumping up then way
down.Other blogs say maybe the TCM sensor or a
reprogramming of the ECM might get it to go off.

Mechanic says bad CAT because of the po420 but
I say no,most likely the MAF sensor (replaced
recently with Bosch OEM) because it's not red hot
nor does my car smell of exhaust or have colored
tailpipe smoke.
Any input would really be appreciated. This car
has sentimental value to me. We picked it out
together back in 02 and my Dad let me drive it off
the lot with 5 miles on it 
Please help