Hi. OK here's my rambling thoughts ... It seems that you're keen for your child to go to the independent school otherwise you wouldn't have looked at route initially.
You say that money isn't an issue at the moment as DH is working. Lets face it - redundancy is a potential for a large proportion of the population, but it's a 'what if'. So I would say if that's what you want - go for it.
If things don't work out down the line and you have to review so be it. Yes it wil be disappointing, disruptive ... but it may not happen! And if it does you'll cope, you'll manage and it won't ruin your DS's life.
Trust me kids are more resilient than you think - I went to about 9 schools, ok I don't have a lifelong network of friends who've been with me since age 5 - but I do have a network of people I know. I learnt the skill of quickly fitting into new situations / roles and I'm able to just get on with whoever I'm with (mostly!), I came out of school with the results I was predicted to get. In other words in restrospect - I don't feel like I it ruined my life at all, quite the opposite.
So I'd say if you can afford it, and want it then go for it. Deal with the now and let the future sort itself out. Just my view.
Best wishes whatever you decide. But I would say please do make your mind up soon. I've got friends with kids waiting to find out if they can go to the same school as their siblings because spaces are limited.
Cheers