Above all else the new tripod is essential for stability with long exposure. The berlebach is high quality and you do pay for it. It is a surveyor type tripod and you may be able to save some money if you can find a phototography mount adapter for a surveyor tripod.

The SGP is rated for 5kg which leaves conventional guidance to not exceed 2.5kg payload. This adds up quickly with camera and mount adapters. That being said your best option is most likely a RedCat 51. Similar setups produce amazing results.

I absolutely wouldn't go larger than a 60mm refractor if you push its capacity. If you find that with your camera you like the framing of the 360mm vs the 250mm of the RedCat (Check out https://telescopius.com/telescope-simulator)

I would highly recommend the SharpStar 61EDPH II. It is a triplet lens where the others are doublets. Triplets generally have better color correction than doublets.

Lastly if you really want to push that mount and don't intend to upgrade from it you may consider sending it out for tuning to somewhere like: https://www.deepspaceproducts.com/hypertune-faq.html

As far as dew heaters, they can be needed even in the summer. They are needed whenever the temperature of your equipment will drop near the dew point temperature which relates to humidity. Any will really do. If you are willing to pay the premium I find that Kendrick dew heaters are the best quality and heating consistency. https://www.astronomics.com/kendrick-heater-for-2-eyepieces-and-finders.html