Struggling

100 g starter 250 bread flour 200 AP flour 10 g salt

mixed at 830p and let BF overnight till 630 am. 10 hours in 68 degree bathroom with door shut (its -20 here currently overnight) baked 450 with lid on for 40 min, 5 minutues uncovered. temped several places to 200/205. I have been doing more stronger of a feed - doing 1:5:5 or so. I want to say I need to push my BF but it is so dang hard with it being so cold. I have been at this for 5 months and my first few loaves (made in oct-nov) always turned out great. Need to be less gummy! Any tips?