John, it's a good idea to stick a thermometer inside the greenhouse to get a firm idea of temps.
Ventilation is not only a good idea on warm days. It's essential to keep air circulating as an aid against fungal diseases. Fungal spores love nothing more than still, humid air.
It's a good idea to remove the lower branches and foliage to keep a gap of 12-18" between the soil and the lowest foliage. It's another aid against fungal problems. Fungal spores can and will drop from the foliage to the soil beneath and can be splashed back up again when watering. The gap helps against this.
You also want to avoid clumps of impenetrable foliage. They work against air circulation, hence offer a haven for fungal spores. Trim branches and foliage judiciously to avoid clumps. Don't overdo it, though, you don't want to remove so much foliage that it threatens the process of photosynthesis.
Nip off the suckers/side shoots, those mini branches that develop diagonally at the intersection of the main stem and its branches.
Don't water by rote. Water when necessary. That means when the mix is dry. Don't keep the mix permanently damp. Few plants like permanently damp roots and toms aren't one of them.
Finally, don't be tempted to overfertilise. In containers, a feed once a month will do the job.
fidgetbones, the mix drying out doesn't cause Blossom End Rot. BER comes about as a result of plant stress, one cause of which can be irregular watering patterns. A regular watering pattern - eg, letting the mix dry out between waterings - is fine. It's when you depart from a regular pattern that a plant can become stressed.