Hello friends, i have recently joined the club and purchased some bitcoins. My opinion of BTC is pretty high and i believe this indeed is the future, and that it would be stupid of me to just ignore it.
So i just recently started but already own 1 BTC and plan to buy a lot more, though it would be irresponsible of me to go into it without any precautions and knowledge. I've read a lot and have a basic grasp of safety but decided to ask some questions as there is a lot of people holding for a long time already and i'm sure people have far more experience than me.

Note that all i want to do with Bitcoin is just store it until 2020-2025. I do not plan on withdrawing the money from this wallet beforehand and i just plan on adding money to it every week or month.

I have completely formatted my PC and disconnected it from Internet to create safe environment to create an Electrum wallet. After doing so i have transferred funds to it, saved the seed phrase and private keys on a brand new pen-drive that i also formatted beforehand just in case. I also have my seed phrase stored in a different safe place in case my pen-drive dies and i cant access it's data. I've put the pen-drive in my safe that is screwed to a wall, so i am technically safe from theft and fire. I formatted my PC once again to erase all data of Wallet being created.

How safe do you guys think is what i did? Is there a possibility of me getting my BTC hacked even though i did all this without internet connection, if i don't compromise the wallet by connecting it to internet?
Is there a possibility in future that 12-seed electrum phrases or electrum private keys stop being accepted by other services, so if Electrum magically dies i'd not be able to recover my BTC?
Is Trezor a better option than what i did there with Electrum? And if so, then how is it better?
Also, assuming i have 10 BTC on my electrum wallet and it's already 2025 where lets say price is 100.000$. It means i can cash-out 1m$.
Do you guys think that i should be using the signed signature thing that lets you pay with offline wallets?
Also i already went through that, and someone did calculations for me on how much it would take to crack electrum seed phrases but is it really so safe?

In case Electrum as a wallet/code/program dies and stop being updated etc. - are my bitcoins still safe? Will my private keys created on Electrum still be available for use on different platforms?