My cat is neurotic and I want to make him feel better

I got my baby when he was around 1m/o as he was born on the street and there were a lot of dangers surrounding him. He had a sister that disappeared a little bit before that. He has grown up to be a very big and healthy 1y4m/o cat. He has always been very crazy and wild. He is very clingy and needy, his games are very rough, but not in the mean way. He usually even purrs when he kicks the hell out of my hand (I know he shouldn't play with my hands but sometimes it's inevitable). He was neutered when he was 7m/o.

I have always been very worried about his behavior, as I fear he is anxious, unhappy and extremely bored. I live alone, I am working a lot and I work on a schedule so I'm leaving and coming back in different times of the day, sometimes I'm gone for 24 hours. I cannot change that circumstance. So usually when I'm at home he has those meowing sessions where he sounds very distressed, he is on edge and seems uneasy and nervous. He also pushes items and opens all kinds of cabinets in a very nervous manner. He would do that for 5 minutes, then lay down for bit and do it again. If I engage with him physically or verbally it's way better - he might start purring, he stops vocalizing, he seems happy and interested at first, but then he loses patience - whether it is for a game or for me holding him. And I cannot always engage with him. When he sleeps he would open his eyes on every noise. Some of these qualities are definitely DNA-based, but others, I fear, are based on understimulation.

Previously, he has become calmer if there was a person with him for 1.5-2 days straight. He would stop doing most of those things. Having someone in the house for more than a day straight has not happened recently so I don't know if it still works like that.

I have been feeling so guilty about all of this since I got him. I'm trying to make it work somehow. So I've been thinking about the following options:

1. Definitely ordering some more interacting/moving toys and scratchy things. Also a bird feeder he could look at from the window.

2. Another cat. It has been on my mind for quite sometime but it is going to be complicated. Will they fancy each other? Will he be too harsh on the other kitty? How is the other kitty going to adapt if I'm missing from home so much? There is this semi-blind male kitty near my workplace, which I have thought of taking home... It is very playful so they might get along and maybe the impaired sight won't be a problem.

3. Calming diffusers - pheromones, CBD... Are they actually good and safe for cats?

4. Try to teach him to go on walks outside (and actually find the time for those walks).

Please tell me what's your thoughts on the listed above and I would be grateful for any other advice!