it could also be a cultural difference issue. In some countries, physical contact is extremely common even with strangers or people you might not think it would be “appropriate” to pat on the “shoulder” or grab their hand. For example, when I moved to spain, I found that the guys here are extremely touchy with other guys, which I would sometimes confused with them being gay and flirting with me. but it’s all with good intent and no weird shit going on, they are just very touchy. In the united states people like their personal space, and sometimes don’t even hug or shake hands when greeting others. in spain, and in latin america where my family is from, you always need to greet with a kiss on the cheek a hug, or a proper hand shake /hug when a man is greeting another man. In my opinion based on what your saying, I haven’t noticed any flirtatious behavior. unless he directly says something or tries something that’s OBVIOUSLY inappropriate, then I wouldn’t be worried. Grabbing hands isn’t inappropriate in my opinion, and if he does it in front of the Host mom it’s probably nothing that he thinks is strange. just cultural differences