Hi HomelyK,
Sorry you are so worried about your little one, it is extremely stressful when you have concerns over development.
There aren't any red flags jumping out at me from what you have described. He is still very young, but what you are describing seems neuro typical. He understands what you are saying, responds to you and is as sociable as can be under recent restrictions.
Your concerns about speech, remember the 12-18 month window sees lot of changes in their development and this is particularly so with language. They are also starting to walk and explore, so you may see some areas of development slow while he is mastering something else, and it will then pick up again. Continue talking/playing with him, sharing with him, reading/singing with him and listening to him.
By 12 months I knew with my eldest something was wrong because he didn't understand anything I said, had no speech or sounds, did not want to engage with people he didn't know. The 12-24 month window of his development highlighted the red flags that signalled autism and learning difficulties.
In contrast ds 2 had early (but not too advanced) speech and understood everything, but wasn't very sociable or interested in others or sharing. I had a gut feeling something was "off" at 8 months with him. We questioned for several years if he was also on the spectrum and as he started nursery/school, his issues became increasingly obvious. He has asd and ADHD.
My dd different again, had very little words at 12 months but after she had mastered walking, her speech really took off.
Keep a note (say monthly) of what he is saying, sounds making and how he is playing. This is helpful if you want to refer back and also makes a nice keepsake to tell him about when he is older and ask you questions about when he was a baby.
I this helps, but if you are that worried please speak to your Health Visitor or GP for reassurance and advice.