We live in Iowa and most houses have an external air conditioning unit and the furnace outlet vents on the side of the house usually side by side.
My question is: Is it safe to park a boat right next to these?

If those vents are low they pose no danger to you or anything near them. That is not to say you should block them with the boat as they need some space. If there was a danger they would be elevated more or have shielding to keep you from putting things close to them. The a/c unit just needs enough clear space around it so it gets airflow to cool the coil.

I have a 2001 Tacoma and plan on towing a small boat with it. I found out that my bumper can hold the weight but I want to know where to install the safety chains, I don’t have any other holes to latch them to other than the chassis.

If the bumper itself does not have any holes in it on both sides of the trailer ball, you can either drill in a couple yourself, have it done or hook the chains under the bumper on the bottom edge. Holes would be best. or place a short set of chains underneath that you could attach the trailer chains to.