Considering this is the prescribed posture for the Our Father in some Eastern Catholic Churches, it can hardly be considered heresy. I personally don’t care much what prayer posture others use, so long as it isn’t especially ostentatious. There are some who argue that because the orans is prescribed for the priest, the congregation may use any prayer posture but that. It’s also suggested by some that since traditionally the deacon said the prayer in place of the congregation, and his posture is to have hands joined, that the congregation should likewise. The simple fact is that a posture for the congregation is not explicitly prescribed, so there is legitimate debate on this at present.
Your second point is a prohibited topic at the moment.
As for your last point, I have heard of the practice of covering or emptying the holy water fonts - this has been prohibited except during the triduum. Even so, it doesn’t constitute heresy, just a misguided practice. Regarding baptismal fonts specifically, since baptisms during Lent are sometimes less frequent and delayed until the Easter Vigil, it may be legitimate to cover the baptismal font alone, if it’s not being used.