[gmonag]

I have towed a 1850kg caravan for many thousands of miles with my 2005 XC90 and could not hope to have a better towcar.
I would suggest that your problems are down to the loading of the caravan. Even if the hitch weight is correct, the distribution of the load can make a massive difference to the stability. Despite your reluctance to discuss the bike rack... you need to remove the bike rack and try again.
Generally the more nose-heavy the caravan, the more stable it is. Load up so that the hitch weight is just below the limit. Avoid weight at the extremes, especially the back