Congrats Emma
It's completely normal to feel worried about things when you are pregnant.
Heavy lifting- don't go crazy and try and lift a trailer or anything (!) but I am sure toddlers would be okay. Other mums with more than one baby would do this sort of thing all the time. Maybe if you get a sore back or feel sick, take it easy.
Where abouts do you live/work that smells like paint often? Is it real or your nose being super sensitive?
There are natural cleaning products that are okay for you (and the earth!) that might help put your mind at ease. Earthwise is one brand, ecostore... I can't remember the other names at the moment.
It's perfectly okay to be worried about things a little bit. Concentrate on eating well and resting. Look after yourself.
I'm sure everything will be okay