Question on protection

I don’t really understand the way this all works. Whenever we have sex, he puts on a condom like halfway through or a couple minutes before he finishes, but always before he finishes. Would there still be precum? I’m not concerned about getting pregnant as we’re ready for a baby, it’s kind of like “we’ll wear them but if it happens it happens”. I was just wondering.

I heard that in all reality male condoms are now thought to be like 85% effective in the first place. What’s the likelihood of getting pregnant in our situation?