I know it is easy for me to say this, but do not worry!
He sounds like he is doing all of the correct things.
I do not know if it is possible to encourage them to crawl or stand as such, just give plenty of encouragement - get on the floor and lie in front of him and encourage him to come towards you perhaps?
With my baby, I 'showed' her the technique for crawling when I was changing her nappy by gently pulling her left arm and right knee towards each other a few times and vice versa. OK, it made her look like a Thunderbird puppet but at least it was preparing her brain for the complicated task of crawling!
Not long after my lo started crawling, she started pulling herself up to standing.
Just to put your mind at rest, your health visitor should do a baby check at around the 8 month mark to check certain developmental milestones.