Long-time reader on the forum, but first time registering and posting; please be gentle


I am just entering the final week of Pete's beginner plan, and have certainly noticed a significant increase in fitness and stamina. The first 5k I rowed was at a split of 2:25/500m and a spm of 28; I was also really tired at the end of it!. My 12k this week was 2:09/500m and a spm of 21 (51:51 time), and although working hard my recovery to normal was pretty quick.
I just have a few questions to you more experienced people, and thought it might be easier to put them in 1 thread:
1. I have done the 3 sessions per week on the plane, which means I am rowing around 20-25km per week now. Is this enough, or should I be doing more?
2. On the longer rows my HR always seems to go to zone 4 and 5 quickly; for context on the latest 12k row I show 14:41 at 142-160bpm and then 34:33 at >160bpm. Is this too high, and do I need to do something differently? Av power on this row was 161 watt, and my normal resting HR is 65bpm.
3. I really want to lose more weight, and have already begun making adjustments in diet etc. Where should I focus my rowing to assist in this area? Ideally I'd like to be training my heart to be fitter too, but am unsure if the 2 can be done together?
4. Finally, where do I go next? It has been hard work to get to the level I am now, and although not quick, am very proud of myself for being able to row the 12k. I'd like to continue to improve fitness, burn fat, and generally keep my heart healthy.
Thanks if you've taken the time to read this, really appreciate it; will answer any questions anyone has.